Apexi N1 Evolution cat-back (70mm - 80mm) on an alll stock S4 N/A.

 

too big, don't waste your time

 

Not really. The biggest power adder in on n/a's is replacing the exhaust manifold. The rest of the exhaust isn't really useful without good headers.

edit: the RB system sounds better IMO and has good results.

 

Well I already have the N1 on. I was asking because I noticed some slight increases in power while I was driving after I had it installed.

I would put headers on, but I plan on doing a TII swap.

 

think of your exhaust like a straw. if you make the end that you suck on bigger your still gioing to suck the same amount through. ive dyno tested a few cat back and actually have seen power loss from stock. start up front and work your way back. and that still wont even make that much more if your not getting more in the engine. so grab an intake while your at it. they both go hand in hand.

 

The stock intake is more than enough for an N/A. Upgrading it will only augment noise levels (not ideal with the N1).

 

if cat backs do increase anything its usually low to mid range torque. theres also the new theory, which is if you expect power gains you will feel power gains. its like a physiological confusion. its like proformance wires when your stock ones are fine.