They don't seem to be very popular. I just found out about them this week while researching how to make my truck sound more like a Corvette. I've seen the videos of people installing equal length exhaust in the GMT800 trucks and that sounds very close. I have yet to hear anything close on GMT900 trucks though. Even after one guy added a trombone loop and some other stuff, it still sounded like a truck. My truck is currently making 575hp with its cam and supercharger setup and I'm very happy with it. Now I wish I could make it sound better. I have 1 7/8" longtube headers, true dual 3" exhaust with resonators and Borla XR-1 mufflers and it sounds okay, could be better though.