On April 2, 2025, EPA Region 1 entered into an Expedited Settlement Agreement (ESA) with Mass Diesel Performance, Inc. (Mass Diesel), full-service auto repair shop based in Bellingham, Massachusetts, resolving 16 violations of Section 203(a)(3)(B) of the Clean Air Act (CAA). The ESA alleged that Mass Diesel sold and/or installed aftermarket emissions tampering devices (defeat devices) for motor vehicles. Under the settlement, which is authorized under the Expedited Settlement Agreement Pilot for Clean Air Act Vehicle and Engine Violations Tampering/Defeat Devices, Mass Diesel will pay a penalty of $14,186 and certify it is operating in compliance with Section 203 of the CAA. EPA, through its direct implementation authority, plays a critical role in addressing tampering and aftermarket defeat device pollutant sources. EPA has notified the Massachusetts Department of Environmental Protection of this matter.