would 2.5 be to big for a a stock f22b1 the exhaust shop sounded hesitant but ive seen fat pipe civics that sound like bulldozers granted they lost power but what would be the optimum size for a power increase but still keeping it quiet and not losing gas milage

 

2 and 1/4 is good enough for a stock f22b1. If you had a built motor or a turbo you could think of 2.5 or 3" exhausts, but in you case, you need back pressure.
And please!! PLEASE!!... don't get rid of your cat converter.

 

Gianinline's got it. End thread.

Simple explanation of why you don't go that big: You'll gain flow (more flow than you need), but lose velocity, which is key to keeping your tq and hp at optimum levels. Especially torque.

 

Or if you have the dough, get a Magnaflow Cat Converter. I'm getting one for my setup(2.5" piping) while I'm getting my Hytech Replica header so I can do them all at once.