Between November 2014 and October 2017, Hartl removed or rendered inoperative emission control devices or elements of design that were installed on or in at least 72 heavy-duty diesel-engine (HDDE) trucks to comply with emission standards promulgated under Title II of the CAA, in violation of Section 203(a)(3)(A) of the CAA. Additionally, Hartl sold, offered to sell, and/or installed engine control module tuning products (ECM Tunes) manufactured by Performance Diesel, Inc. (PDI), that had the principal effect of bypassing, defeating, or rendering inoperative the emission controls and emission-related elements of design on these 72 HDDE trucks, in violation of Section 203(a)(3)(B) of the CAA. EPA uncovered these violations through a Request for Information issued under Section 208 of the CAA on November 6, 2017, to which Hartl responded on January 12, 2018. EPA issued a Finding of Violation (FOV) to Hartl on March 15, 2018. Hartl Diesel, LLC and Mr. Hartl certified that as of May 11, 2018, they are no longer selling or installing ECM Tunes by PDI. This CAFO requires Hartl to pay a penalty of $3,600 and certify that Hartl Diesel, LLC and Mr. Hartl will not remove or render inoperative, or manufacture, sell, offer to sell, or install any part or component to bypass, defeat, or render inoperative, any emission control system or element of design on any vehicle, and resolves the FOV issued to Hartl on March 15, 2018. Hart will also notify customers of the settlement with EPA and o