For those of you who have seen, I recently got an 08 Cobalt Sport. What is there to add to increase horsepower? Other than a turbo/supercharger? It already has one of those obnoxious mufflers, I'm not sure if that did anything or not.
If you want to get the most out of your car without going forced induction then your best Bret is to get the things on this list..
-header
-downpipe
-catback exhaust
-intake
-upgraded tranny/engine mounts
-trifecta tune/HPTuner