Ls exhaust

How big should the exhaust be in a civic with a b18a1 swap? My car came with the Flowmaster cat-back with 2" piping, will this affect performance? Thanx for all help.

For a N/A motor I'd say that's find. Most civics that run aftermarket pipes are running 2.25", and maybe 2.5" with a turbo, or a little bigger. But you should be fine unless you are pushing some serious horse power out of your engine.