Well, I have installed my JRE 4" exhaust. I have noticed the decrease in egt and quicker turbo spool up, however, the sound seems to be a bit on the "airy" side. When I really stomp on her it sounds pretty good, but cruising around town it just sounds like I'm blowing hot air. I know another guy who kept his stock pipe, but removed his cat and muffler and his sounds much better. (more like the big rigs). I haven't installed my "Scotty" air yet, but hope to tonight. Overall the quality of the JRE system I believe is second to none. Any comments are welcome.