personally i'm not a fan. i think M3s shouldn't be tampered with.
also, if it's not illegal, it should be. having ridden behind a pickup truck with a chrome plated tailgate, at night, with a migraine...it's hell. your lights shine back in your eyes no matter how far back you get. ( i was on a two lane road with no passing oppurtunities to clarify why i didn't just get away from the guy)