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Press Release

Idaho Diesel Parts Companies and Owner Agree to Pay $1 Million After Pleading Guilty to Selling and Installing Illegal Defeat Devices

For Immediate Release
U.S. Attorney's Office, District of Idaho

POCATELLO – Diesel performance parts retailers GDP Tuning LLC and Custom Auto of Rexburg LLC, doing business as “Gorilla Performance,” as well as the companies’ owner Barry Pierce, pleaded guilty to criminal charges today in federal court in Pocatello, and agreed to pay a total of $1 million in criminal fines, announced U.S. Attorney Josh Hurwit today.  The companies also agreed to implement compliance programs and to not manufacture, sell or install any device that defeats a vehicle’s emissions controls.  

GDP Tuning pleaded guilty to an information charging it with conspiracy to violate the Clean Air Act (CAA).  Gorilla Performance and Pierce pleaded guilty to an information charging them with violating the CAA by tampering with the monitoring device of an emissions control system of a diesel truck.  Under the plea agreement, the companies and Pierce agree to pay a $1 million criminal fine.  Pierce also faces up to 2 years in federal prison.

“The defendants in this case purposefully violated laws that protect air quality and the overall quality of life for Idahoans, especially vulnerable populations such as children, the elderly and those who suffer from respiratory conditions,” said U.S. Attorney Josh Hurwit.  “My office will continue to partner with law enforcement agencies to prosecute those who seek illegal profits at the expense the public’s health and our shared environment.”

“Tampering with vehicles’ on-board diagnostic devices isn’t just a violation of federal law – it’s a major health hazard,” said Assistant Attorney General Todd Kim of the Justice Department’s Environment and Natural Resources Division. “People are harmed as a direct consequence of the many air pollutants that would be removed by emissions controls systems absent the illegal tampering. We have made progress in curbing harmful emissions, but that progress is undermined by sellers and distributors of defeat devices. We are committed to enforcing the Clean Air Act and holding accountable businesses and individuals that violate federal law.”

“Nearly a decade after EPA began cracking down on illegal defeat devices that violate the Clean Air Act, there is no excuse for companies to be continuing to cheat on vehicle emissions and putting the health of the environment and our communities at risk,” said Assistant Administrator David M. Uhlmann for the Environmental Protection Agency’s (EPA) Office of Enforcement and Compliance Assurance. “EPA will continue to pursue criminal charges against companies like Gorilla Diesel, which broke the law brazenly and repeatedly, until this egregious criminal activity comes to a stop once and for all.”

According to court documents, GDP Tuning conspired with its owner Barry Pierce and others to violate the CAA by purchasing and selling tens of thousands of tuning devices and accompanying software which, when used together, tampered with vehicles’ on-board diagnostic (OBD) systems.  OBDs normally detect any removal and malfunction of a vehicle’s emissions control equipment and record a diagnostic trouble code which will illuminate a vehicles “check engine light.”  If the malfunction is not remedied, some vehicles can go into “limp mode,” where the maximum speed is limited to 5 mph as an incentive to have the vehicle repaired.

GDP Tuning bought and sold devices and software that allowed customers to reprogram or “tune” a vehicle’s OBD.  This reprogramming tampers with emissions monitoring built into the diagnostic system and allows removal of the vehicle’s emissions control equipment without detection by the OBD.  Removing a vehicle’s emissions controls is typically referred to as a “delete” and is accompanied by a “delete tune.”

In addition to GDP Tuning’s national wholesale operation, Gorilla Performance and Pierce operated a retail shop and auto repair facility in Rexburg, where customers’ trucks were deleted and tuned.

Diesel exhaust contains a variety of air pollutants, such as particulate matter (PM), nitrogen oxides (NOx), carbon monoxide and non-methane hydrocarbons, among other hazardous air pollutants. Factory-standard emissions control equipment dramatically reduces these emissions. 

Deleting a diesel truck causes its emissions to increase dramatically.  For a fully deleted truck with all emissions equipment removed, EPA testing has quantified the increased emissions as follows: NOx increased 310 times, non-methane hydrocarbons increased 1,400 times, carbon monoxide increased 120 times and PM increased 40 times.  EPA’s Air Enforcement Division released a report in November 2020 finding that more than 500,000 diesel pickup trucks in the United States – approximately 15% of U.S. diesel trucks that were originally certified with emissions controls – have been illegally deleted. 

Diesel emissions contain multiple hazardous compounds that harm human health and the environment.  Diesel emissions have been found to cause and worsen respiratory ailments such as asthma and lung cancer.  One study found that 21,000 American deaths annually are attributable to diesel particulate matter.  Additionally, exposure to polluted air in utero has been associated with a host of problems with lifelong ramifications including low birth weight, preterm birth, autism, asthma and brain and memory disorders.  

The defendants are scheduled to be sentenced by Senior U.S. District Court Judge B. Lynn Winmill on Nov. 8.  Though the corporate defendants agreed to pay $1 million in criminal fines under the plea agreements, they face a maximum fine per count of $500,000 or twice the gross pecuniary gain derived from the offense, and Pierce faces up to 2 years in prison.  The defendants’ sentences will be determined at the discretion of the court after application of statutory factors and the Federal Sentencing Guidelines, which consider a number of variables.  

The criminal case stemmed from an investigation by the EPA’s Criminal Investigation Division.  U.S. Attorney Josh Hurwit, Senior Trial Attorney Cassandra Barnum of the Justice Department’s Environmental Crimes Section, and EPA Regional Criminal Enforcement Counsel Karla Perrin are prosecuting the case.

Stopping the manufacture, sale, and installation of illegal delete devices is a priority for EPA.  To learn more, visit:





Public Information Officer

(208) 334-1211

Updated August 23, 2023