Originally Posted by tank the ek
Don't mean to wake up an older thread, but was the choice of the stock cat-back for the sake of noise, or was there another determining factor? Kind of curious if there could be anymore power pulled out of this with a larger/aftermarket catback, and how much.
Yes, it was simply to keep it quiet. I switched to the GReddy Ti-C exhaust (3.15" piping, N1 style muffler) and Virtual Dyno showed that it gained around 20WHP, but it was a little loud for me.
Since then I switched to the GReddy SP Elite (quad tip, much quieter) and the Invidia EL header. Recent logs still show me about 20-25WHP higher than when I dyno'd with the stock header and stock exhaust.
From what I've seen, the stock cat back is pretty decent, but at 400+ WHP it does start taking a little power away. Most all of the 3" options will do fine at that point. An N1 style can is going to be best, but it's not a huge difference.