[2four2]

I'm regularly involved in the car community, and this is far more common than is often thought. I've met dozens of people who have illegally modified their diesels, and that's in California. There's plenty more for the EPA to crack down on.

[Washuu]

Car modders toss catalytic converters all the time too in states without emissions enforcement. It's just not a problem that is handled.

At one point I was working on a startup idea that would produce a piece of electronics for helping with drive train swaps. However, I realized that it would make it very easy to ignore all emission and safety requirements despite my efforts to prevent that. So I dropped the entire idea and moved on with my life. I don't want to unintentionally help other people make the planet worse.(But I also wanted people to reuse/recycle car parts more effectively. Oh well.)

[car]

What kind of modifications are these? EGR and DPF deletes? That would surely be caught during California Diesel smog testing.