The QTP cutouts are pretty easy to put in if you have a stock exhaust. If you have an after-market exhaust and you have an LS3, then they fit pretty well right behind the headers (where the cats would go). However, I have an L99 and an after-market exhaust, so they couldn't get the round QTP cutouts to tuck up high enough (the transmission pan takes up more room in an L99 and doesn't allow the cutouts to tuck up in high enough). This was only a problem because my car is lowered and we were afraid the cutouts might bottom out on speed bumps. So my shop had to do some extra masterful fabrication work to get them to fit, but they did it. Here is video clip for you. I LOVE the sound, but when they are open, they are stupid loud. But, they are really fun to open when someone in the adjacent lane at a red light starts revving his motor.