Attn Greddy and Stock Manifold users
 

Well I have the Greddy Header on my S14 and for those who dont know it retains the Factory Pre Cat. Enter the SR20 Downpipe. It Deletes the Pre Cat and All s13 and s14 Dohc Downpipes are the same. A friend of mine has Stock Exhaust Manifold and we took his Pre Cat off and hooked up a Down Pipe and I have to tell you the Power increase felt the same as Putting on a full aftermarket Manifold. And the cool thing is we got both Downpipes from guys who did SR swaps for 20 bucks. Something for those to consider on a budget. I'll have pics in the next 2 days.

So, would it do good to run a down pipe with a 2.5in pipe to the muffler? By the way, whats a good type of muffler for side exhaust?

Even a Stock SR20 Downpipe would be Benificial for you if you have 2.5 in Exhaust. But as far as a good Muffler to use for Side Exhaust, I think Magnaflow makes the best Sounding Mufflers.