Everyone has something different on here,I prefer custom exhaust work,its cheaper and same thing as a cat-back honestly.Always the option to choose the muffler you want.Honestly the exhaust system gives you tiny gains,nothing big.When you get a new intake,header, and downpipe with that cat-back.Then you will notice the major gains a 2.2 has.I know you have the air box mod,but I prefer better throttle response from my K&N intake and cleaning my filter.
2006 Chevy Cobalt LT
K&N air intake system
Custom 2.5" dynomax exhaust system
B&M tranny cooler
stainless steel pacesetter header
5900k light bulbs
2.4 intake manifold