So i'm thinkin of doing a little custom exhaust work, my friend's dad owns a shop so i can get the parts at price. Tell me how this sounds.

3" downpipe
stock cat (high flow too expensive for now)
2.5" piping
magnaflow muffler

 

You wont gain as much torque with a 3" downpipe and it is to big for a k03. I would say get a testpipe, 2.5" or 2.75" if you can get one custom made, i've read that that would be the best size testpipe and a full 2.5" all the way back. I have a 3" testpipe and i did notice a gain in high end HP and a little tq., but i hit full boost at like ~2.3k.

 

sorry, i should have mentioned i'm upgrading to a ko4 hence the new exhaust. Would a 2.5 or 2.75 test pipe still be better for a ko4?

 

I have heard that a 2.75" test pipe would work great with a k04 but it would have to be custom made. They make 2.5" and 3". I believe the exhaust side of the k04 is a 2-5/8" exit. I could check but im lazy at this time of night.