EPA defines tampering here: Tampering. You may not remove or render inoperative any device or element of design installed on or in engines/equipment in compli

EPA defines tampering here: Tampering. You may not remove or render inoperative any device or element of design installed on or in engines/equipment in compliance with the regulations prior to its sale and delivery to the ultimate purchaser. https://www.ecfr.gov/current/title-40/part-1068/section-1068.101#p-1068.101(b)(1) https://www.ecfr.gov/current/title-40/part-1068/section-1068... It seems primarily about bypassing or disabling emission controls, not user controlled fuel mapping, or mods like putting in a performance air filter or exhaust. But EPA does consider a flex fuel conversion tampering. https://afdc.energy.gov/bulletins/technology_bulletin_0807.html https://afdc.energy.gov/bulletins/technology_bulletin_0807.h...