> My understanding is that such parts are not by themselves illegal. The crime is actually using them on the road. My understanding was that they were legal for track purposes.
That certainly used to be the case, but it changed recently, and the EPA has been aggressively going after anyone who sells them for any purpose.
If you're in the US and sell things that can modify emissions stuff, they're coming for you. Period.
Omitting wear and reliability concerns, some tunes gain their effect by not controlling for things like NoX and unburned hydrocarbons.
The worst offenders? "Coal rolling". It would be one thing to do this to help spool a turbo or for some other performance reason, but it's literally running the motor as rich as possible to dump unburned fuel out the tailpipe to make a visual effect. At the expense of everyone around you.
It does, but it's worth noting that a manufacturer of such devices can make it meet federal emissions regulations (if they want to spend the $$$$ on R&D), and they can sell devices that are 100% legal in all 50 states.
Examples are Green Diesel Engineering (Who did a TON of dyno time and used to work for a major OEM on emissions stuff) and Banks (who are virtually an OEM at this point)
That certainly used to be the case, but it changed recently, and the EPA has been aggressively going after anyone who sells them for any purpose.
If you're in the US and sell things that can modify emissions stuff, they're coming for you. Period.