Originally Posted by Icemark

On a non turbo ideally you want a 2" to 2.25" down pipe or header, but you do not want to be bigger than 2.5 inches until after the point where the back end of the cat would be. After the back end of the cat (or the front of the y-pipe) you can go up to a 3" single or two 2"- 2.5 inch duals. Anything bigger will reduce the power.

Originally Posted by HeyITZthatFC

Is there a significant difference between a 2"-2.25" compared to a 2.5" (I know you said ideally, so I'm guessing there is a little difference right?) running to a 3"? I'm still looking around

Originally Posted by Icemark

when I was building exhausts for the non turbo FC and dynoing them, I didn't see any really big drop off until around 60mm (2.35"ID), other wise it was pretty much the same between 50mm to 2.25 (ID).

Originally Posted by Omixeo

Pay no attention to the crappy drifting, lol.

RB header, test pipe, corksport 3" catback. I'm sure they heard me miles away.

http://ca.youtube.com/watch?v=m2B7Kxr8vPE