I have a 93 Prelude VTEC that is in the process of being boosted. Now, I would love to put a 3" exhaust on it, but guess what, no one makes it, so I will have to get it custom made. Well, here is where the question comes in. I have a 2.5" Downpipe. I am working with limited funds right now, or I would of had Art make me one. But how much performance will I see from a cat and cat back 3" exhaust with a 2.5" Downpipe. How would 2.5" All the way back be? I know the more flow you get the better, but I am looking at a grip to get it done and I am just making sure it is worth it!

 

May as well do the 3" now. With a 2.5" downpipe. Then when the time comes you can go to a 3". YEs a 3" exhaust wil be beneficial even with 2.5" downpipe.