I had the ebay exhaust that clones the borla/gmpp on mine. Sounds really good paired with the zzp shorty header and 2.5" catted downpipe. It made the pop sounds during downshift. The only bad it had was a sleight rasp between 3200-3700rpms during acceleration.
2009 Cobalt LS XFE U74
Mods: K&N Typhoon Intake, Option Cat-Back Exhaust, Cosmo Short shifter, Maxxim Ahead 17X7's, MPx shorty antenna, FE5 Strut/shocks, Tein S Techs, Moog endlinks, Moog spring seaters, ZZP shorty header, LSJ downpipe, LNF front grille