Ten years ago, the EPA’s Diesel Tune Competition regulations weren’t much of a concern for the dozens of tuners and truck owners who calibrated diesel trucks in their shops. They could sell exhaust systems, handheld tuners, and other products that increased tailpipe pollutants without raising red flags. Then, around three years ago, the EPA started cracking down on emissions “defeat” devices in an attempt to keep the nation’s vehicles cleaner. Parts suppliers, race shops and tuners have seen their revenue and profits plummet since then, with many facing millions in fines for violating EPA guidelines.

The EPA’s crackdown hasn’t been a one-size-fits-all affair, though. Some tuners specializing in certain vehicles have been targeted while others remain out of the crosshairs altogether. We recently spoke with several diesel performance professionals from a wide variety of companies who have been hit hard by the EPA’s National Compliance Initiative (NCI) to get their take on what’s going on.

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Some like Kory Willis, founder and lead tuner at PPEI, are attempting to stay legal. His company’s current catalog includes a line that says, “CARB EO number pending.” All of PPEI’s tunes are developed to work with trucks whose emissions control devices remain intact and haven’t been modified, which will allow them to avoid the hefty fines other aftermarket companies have faced.

Another tuner staying out of the EPA’s crosshairs is Gale Banks, who has operated his Banks Power business in California for nearly 50 years. He was instrumental in bargaining with CARB to create the code that allows companies like his to modify compression-ignition diesel engines while still remaining legally compliant.