Diesel Emissions Scheme Exposed: Noteworthy $3.1 Million Penalty & 10 Critical Insights

Uncover the Diesel Emissions Scheme shaking up the diesel aftermarket—and how once-popular “delete tunes” have vanished from legitimate sales.
Explore new strategies that leading tuners use to achieve emissions-intact performance while staying compliant with the Clean Air Act.
Learn the real costs behind CARB certification rules, criminal fines, and the hard pivot away from aftermarket defeat devices.

Diesel Emissions Scheme Exposed shown by White box-truck at a gas station with a green canopy under soft pastel skies.

The Diesel Emissions Scheme has become one of the most scrutinized areas of automotive performance.

The Diesel Emissions Scheme has become one of the most scrutinized areas of automotive performance, especially in light of recent enforcement actions targeting aftermarket defeat devices. From substantial fines to new compliance requirements, federal authorities have reshaped how diesel tuners operate. Below is a structured, impartial synopsis of developments through 2025, focusing on Power Performance Enterprises Inc. (PPEI) and the broader diesel performance aftermarket.

Diesel Emissions Scheme in Focus

1. PPEI’s Reinvention and Post-Sentencing Reality

PPEI was once synonymous with “delete tunes”—software designed to remove or bypass factory pollution controls like the diesel particulate filter (DPF). Following federal charges for violating the Clean Air Act (learn about the impact of the Clean Air Act on diesel regulations), the company and its owner, Kory Willis, faced sizable emissions tampering fines (implications of a criminal record in the trucking sector). By late 2024, PPEI entered a plea agreement, resulting in criminal and civil penalties totaling $3.1 million.

Sponsorship

Under a court-imposed compliance program, PPEI can no longer sell hardware or software that disables emissions systems. Instead, it offers emissions-intact performance calibrations—see the latest developments in Clean Diesel technology. These tunes preserve factory exhaust after-treatment components while boosting horsepower and torque. Marketing materials now stress that these products maintain pollution controls, reflecting a pivot toward Clean Air Act compliance.

2. Shifting Product Lines and Marketing

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Power Performance Enterprises Inc. (PPEI)

PPEI’s transformation shows how a business can rebound by prioritizing Clean Air Act compliance.

PPEI’s online store has removed all references to “delete” or “off-road-only” tunes. The revised website explicitly states that any calibration sold is designed for vehicles with fully functioning emissions components. Purchasers must confirm they have not removed factory equipment, and PPEI reserves the right to cancel orders suspected of tampering.

The company also aims to secure CARB certification rules approval (via Executive Orders) for multiple engine platforms, including GM Duramax and Ford PowerStroke. Each tune is labeled “CARB EO pending,” signaling a desire to be street-legal even in states like California. Though the certification process is expensive—often tens of thousands of dollars per engine family—PPEI views compliance as essential for long-term survival.

Recent PPEI Developments

3. Final Sentencing and Legal Outcomes

Despite earlier anticipation of sentencing in 2022, final rulings were handed down in December 2024. The court ordered PPEI and Kory Willis to pay $1.55 million in criminal fines plus $1.55 million in civil penalties. Willis received three years of probation, with the first 10 months under home detention. PPEI is under five years of organizational probation.

Per EPA enforcement trends (EPA’s latest enforcement efforts), the case is considered one of the largest actions against a single company for aftermarket vehicle modifications that circumvent emissions controls. Prosecutors highlighted PPEI’s extensive reach, with an estimated 175,000 vehicles tuned and monthly revenue once exceeding $1 million.

4. Compliance Obligations and No Further Appeals

Close-up of a truck with another following close behind

Regulators maintain that if a product is likely to be used on public roads, it constitutes illegal tampering.

The DPF delete crackdown has forced PPEI to destroy remaining delete devices, issue notices to dealers, and train staff on new procedures. Publicly, Kory Willis acknowledges that any additional violation during his probation could trigger further federal action. Given the negotiated plea agreement, appeals are unlikely. Both the criminal sentence and the civil consent decree leave no legal gray area: PPEI may not sell or facilitate any “defeat devices.”

So far, there is no sign that PPEI plans to contest the settlement. Instead, it has embraced the notion of diesel tuning compliance (federal and state-level Regulations shaping the industry) as a new business model. Company statements and disclaimers emphasize a permanent move away from illegal modifications.

Sentencing Overview

5. Industry-Wide Ramifications

PPEI’s penalties echo a wider pattern of federal environmental oversight. Other well-known entities—Sinister Diesel, Thoroughbred Diesel, and Diesel Freak LLC—faced similar or steeper consequences. These outcomes underscore that no region or business size is immune from inspections and potential criminal liability.

Sinister Diesel (California): Paid $1 million in fines and must cease manufacturing any defeat device components.
Thoroughbred Diesel (Kentucky): Settled for $1.25 million, removed all references to deletes on its website.
Diesel Freak LLC (Michigan): The company and individuals faced criminal charges for systematically disabling emissions on commercial trucks.

Collectively, these cases form a strong message: the federal government is resolute in halting the Diesel Emissions Scheme across state lines.

6. EPA’s National Compliance Initiative

Artistic render of a Rig transporting on road

From multi-million-dollar fines to probation, illegal deletion of diesel emissions devices comes with steep penalties.

Since 2020, the EPA has ramped up its National Compliance Initiative to stop aftermarket defeat devices. Over 170 civil enforcement cases have been finalized, with total penalties reaching $55.5 million. Additionally, at least 17 criminal cases have included $5.6 million in fines and 54 months of collective incarceration.

Officials argue these measures protect public health and preserve the effectiveness of factory pollution controls. The EPA cites research indicating that widespread tampering has produced hundreds of thousands of tons in excess nitrogen oxides (NOx) emissions. This heightened scrutiny means any attempts to bypass or remove DPF, EGR, or SCR systems are likely to attract swift enforcement.

Enforcement and Compliance Trends

7. Broader Landscape of Diesel Tuning Compliance

Major tuning brands that once marketed “race only” solutions have pivoted. Some, such as H&S Performance, shuttered years ago. Others, including Edge Products and Bully Dog, entered consent decrees. A handful—like Gale Banks Engineering—had always prioritized emissions-intact performance, touting the feasibility of generating power without polluting.

Today, disclaimers alone (e.g., “for off-road use only”) fail to protect manufacturers. Regulators maintain that if a product is likely to be used on public roads, it constitutes illegal tampering. Consequently, many companies have cleansed their catalogs of outright delete hardware. PPEI’s approach is emblematic: prospective buyers must affirm that their trucks remain factory-equipped, with a restocking fee if the statement proves false.

8. The Path to CARB Certification

We’re witnessing a major shake-up in the diesel tuning landscape as off-road loopholes vanish.

To survive in this regulatory climate, tuners seek official validation. Gaining a California Air Resources Board (CARB) Executive Order for each engine family is an arduous process involving emissions testing that can cost $50,000 or more per certification. Yet a CARB EO provides legal clarity in all 50 states and fosters consumer trust.

Kory Willis admits these tests increase overhead significantly, but notes that offering fully verified products is the only way forward. This shift is transforming the diesel performance aftermarket: smaller “mom and pop” shops struggle with testing costs, while larger companies with capital to invest in R&D stand to dominate.

Industry Reactions

9. Competitors Adapt or Exit

The new enforcement reality has led to an industry shake-up. Competitors to PPEI either adopt similar Clean Air Act compliance strategies or risk investigations. Some shops keep a low profile, remove references to “delete,” or quietly exit the business. Others pivot to different specialties, such as suspension or aesthetic modifications, to avoid potential legal pitfalls.

A handful of established brands, like Banks Power, emphasize that they have been “clean and legal” for decades. Their product lines integrate easily with factory systems, and they often highlight that significant horsepower gains are possible without removing pollution controls. These businesses now stand out as stable and forward-thinking, gaining traction as customers seek tunes that won’t jeopardize warranties or fail state inspections.

Shifts in Diesel Tuning

10. Community Response and Market Behavior

Customers want horsepower gains while keeping the factory emissions system intact—federal rules now demand it.

Within the diesel enthusiast community, reactions range from defiance to acceptance. Many owners still resent federal oversight, arguing that removing or bypassing emissions devices can boost reliability. Others welcome the clampdown, citing the negative press around “rolling coal” and its environmental harm.

Discussions across forums reveal that potential buyers weigh legal compliance against the appeal of a simplified exhaust system. They also note a “gray market” surge, where older tuners or secondhand devices that enable full deletion sell at inflated prices. However, numerous states now enforce stricter inspections, making it risky to operate a fully “deleted” truck. Commercial fleets, in particular, must remain cautious after seeing large-scale crackdowns on trucking operations.

Customer Sentiment

PPEI’s loyal fan base largely supports Kory Willis, praising his willingness to fight the EPA enforcement trends. Some community members fault the government, claiming “big brother overreach.” Others applaud the settlement, believing it curbs air pollution and levels the playing field for businesses that have always been legal.

Owners who once purchased delete tunes from PPEI often speak positively of the company’s pre-2020 offerings. Yet many now endorse the brand’s newer emissions-friendly calibrations, noting decent horsepower gains and fewer DPF regenerations. Reviews from cross-country haulers and daily drivers indicate that the revised PPEI tunes balance power with reliability—an outcome that suggests compliance need not mean sacrificing performance.

Implications for the Future

Gaining California Air Resources Board approval can cost $50,000 or more per engine family.

While the Diesel Emissions Scheme crackdown has met significant resistance in certain enthusiast circles, the legal framework is unlikely to shift in the short term. Efforts like the RPM Act, championed by industry groups, remain stalled in Congress. As a result, new or revitalized businesses must invest in diesel tuning compliance to avoid massive fines or criminal charges. (Explore penalties for Violations in aftermarket modifications and various Penalties driving industry-wide compliance.)

In the coming years, expect more merger activity among tuners, consolidated R&D budgets for CARB certification, and an ongoing emphasis on off-road tuning restrictions. For diesel owners, the “delete era” is essentially over in mainstream retail. Any lingering black-market activity carries heightened legal peril. The path forward involves developing advanced calibration techniques that retain all factory pollution controls while still unlocking torque and power.

Industry at a Crossroads

While large, well-funded tuning companies can absorb testing expenses and meet stricter Clean Air Act standards, smaller shops often lack the resources to pursue costly CARB certification. This imbalance may accelerate market consolidation, with big players dominating emissions-compliant technology. Yet innovation could flourish as more tuners invest in research and development. Ultimately, every business faces a pivotal choice: pivot toward lawful, emissions-intact solutions or risk steep penalties under heightened EPA enforcement.

Conclusion

Aggressive EPA enforcement has pushed the ‘delete era’ underground, leaving legal tunes as the only viable path.

The evolving Diesel Emissions Scheme underscores a fundamental change in the diesel tuning landscape. PPEI’s transformation from a leading delete-tuner to a stringent compliance-focused enterprise is a microcosm of the broader DPF delete crackdown. Spurred by major fines, probation terms, and the threat of additional enforcement, PPEI now represents how a business can rebound by prioritizing Clean Air Act compliance.

For enthusiasts, this represents both a challenge and an opportunity: the days of unregulated modifications are fading, yet the push for legal, high-performance calibrations is stimulating innovation. From EPA enforcement trends to the quest for CARB certification rules, the industry’s route forward is clear. Diesel tuning is here to stay—just not in the same form it was before 2020.

Compliance, reliability, and legitimate performance gains now drive the market. Whether customers embrace or resent these rules, the result is a reshaped diesel aftermarket that merges horsepower and cleaner air under a more scrutinized regulatory framework. And for further context on the shifting landscape, don’t miss these emerging issues within the Trucking Industry.

Key Developments in the Diesel Emissions Scheme

Major Legal Actions: Multi-million-dollar fines, probation terms, and permanent injunctions have forced top tuners to cease illegal delete products.
Shifting Industry Landscape: Many brands now emphasize emissions-intact performance, investing in CARB approval for new tunes that boost power legally.
Community & Market Reaction: Enthusiasts remain divided; some call it government overreach while others see cleaner air and safer legal options for diesel performance.

10 Critical Insights into the Diesel Emissions Scheme

Record-Setting Fines and Probation: Enforcement agencies have imposed hefty penalties—including multi-million-dollar fines and probation terms—on companies like PPEI for selling or facilitating illegal defeat devices.
Compliance-Driven Business Pivots: Former “delete tune” providers are rebranding to emphasize emissions-intact calibrations, seeking to retain customers without violating pollution standards.
CARB Certification Challenges: Gaining approval from the California Air Resources Board can cost tens of thousands of dollars per engine family, creating a high barrier to legal aftermarket performance.
Industry-Wide Scrutiny: Not just tuning giants—smaller shops and distributors have been targeted by EPA enforcement, illustrating that no segment of the diesel aftermarket is immune to federal oversight.
Off-Road Label Loopholes Closed: Traditional disclaimers like “for off-road use only” are no longer a shield; regulators hold manufacturers accountable for products likely used on public roads.
Shift in Customer Expectations: Diesel owners now look for drivability and horsepower gains that maintain factory emissions hardware, reflecting increased awareness of legal and environmental concerns.
Long-Term Market Realignment: As illegal operators exit or pivot, larger, capital-backed companies offering emissions-compliant solutions gain traction and shape the future of diesel tuning.
Legal Risks for Fleet Owners: Commercial truck operators face potential prosecution for conspiring to delete or tamper with factory emissions systems, signaling broader accountability beyond parts sellers.
Evolving Forum and Social Media Culture: Enthusiast conversations reflect growing caution around openly discussing or displaying deleted trucks, highlighting the chilling effect of government crackdowns.
Implications for Future Regulations: Ongoing enforcement underscores a possible precedent for even tighter federal and state controls, pushing the diesel aftermarket to innovate within the law.