I'm am completely stock what mod should I do first badmab header or ZZP downpipe?

And if it is downpipe should I get 2.5" or 3"?

 

you should sell your cobalt and buy a hyundai

 

how about intake? lol if not go dp

 

do downpipe together with header. save for both at once at least.
also intake would help

 

Intake then maybe header and dp.

 

Intake first, then header & downpipe together.
I did Injen intake, badmab header, & ZZP 3" Catless DP and no complaints here other than wanting to upgrade to a 3"intake.

 

I already have a k&n drop in and a hacked airbox so my intake is good for now.
That's why I'm choosing exhaust stuff now.

BTW I have a redline not a cobalt

Plus intakes on our cars don't do much besides for supercharger whine

 

longtube header, 3in catless dp. /thread.