i was wondering if it would make a difference if the muffler inlet diameter was larger than the exhaust piping diameter. Other than bolting problems. Everything is stock right now i was wondering if i would need to redo the whole exhaust system, and it doesnt have a turbo and probably wont

 

you'll be fine, my friend has a 2.5" back to a 3" muffler and tailpipe on his NA crx, works fine...

 

As long as you're not going from 3.0 down to 2.5