Z1 Exhaust comparison vid
 

Not real comprehensive but worth checking out. Makes me wonder what catback would be best for my 634whp sc car... I know it can't be what's on it.

https://youtu.be/5m22XYHNNeY

I run the HKS Hi Power and made a lot more than 634 supercharged and mid 700's with tt's

That's good #s. I just wish I could sell the one that's on it and that either Greddy would be in stock for under 1200 like several sites have it for ot the hks was down in that price range... I don't mind the Borla sound with headers and test pipes but it makes no sense going from 2.5 test pipes to 2.25 borla not to mention I know other systems could give a few hp more not that I really need it.

The HKS is advertised as a 2.50" but it's actually a little smaller than that but it flows pretty well. When my car was supercharged, my tuner disconnected the exhaust to see how much of a restriction the HKS was. It only gained 10whp with it disconnected. That showed in Z1's test too.