ahahah LACK of backpressure!! All Gibson exhaust systems are 50 state legal and the lack of back pressure is BS. The lack of scavaging or exhaust velocity, ok, but back pressure is bad, umkay? My friend put the same set up on this 98 Silvarado, and there was ZERO problem with his car. There are tons of people who do it, and I have never heard of such a problem.