Who has a turbo AND knows what they're doing AND told you that?

 

I used to have a Probe before my Civic, and as we all know, first gen Probe GTs were turbo. They had a 2.2 L turbo engine, and most guys generally ran around 10-15lbs of boost. They had larger displacement engines than your civic, ran a hell of a lot more boost on those engines than you will on your civic, yet the univerally accepted diameter for exhaust piping was 2.5". You can go ahead and get 3" piping if you want it, but its going to be overkill. It might make you a little faster up top and give you a higher top speed, but it will slow you down down low, and with the lack of torque that civics have, do you really want to be any weaker down low??

 

Thats what happened with my friends civic, what str8edgexx said. He was running low boost amount, but got a 3" pipe, and it dragged low speeds. then he got a 2.5" and it balanced the low/top speeds nicely. I guess it really just depends on your boost amount.