i know this is kinda disputed but what the heck. i'm gonna be running a 14b at 8-10 psi. it'll have a front mount intercooler from johnnyracecar.com. i have all the stuff except the pipes. it has a 2.25" magnaflow catback. i was figuring to just go with 2.25" for the charge pipes and downpipe to make things easy with buying the material.

also would it be worth making a separate downpipe for the wastegate and tieing it in down a foot or so.

 

I would go with 2.5 inch because your IC has 2.5 inch holes in it and your TB is that size too... well mine is anyways.

 

ya for both of those. would there be any performance benefit to 2.5" maybe more lag? not that it's going to cost me that much more but would it be worth my money?

 

for a turbo'd civic I wouldn't go any smaller than 2.5" for exhaust piping. Period.