I did extractors, 100cel cats, custom 2.5" pipes, j-pipes, sports muffler. Sound is amazing. 0 drone all through the rev range, and properly beefy when you hit the juice. I've got a similar system on the Clubsport but it's nowhere near as good. I don't know if it's the j-pipes or the aftermarket vs HSV headers that makes the difference but it's night and day.