Comment by Arainach
12 hours ago
One person's "controlling their own engines" is another "spewing nitrous oxides, carbon monoxide, and other pollutants into the air, giving cancer to neighbors and destroying the atmosphere". We tried the "don't regulate" path and it ended in a multitude of disasters.
You can regulate emissions without preventing custom tunes
In practice, no, you can't. Certainly not without enormous costs such as mandatory regular vehicle inspections.