I'd rather contact a company personally just before tossing out a shot in the dark.
I'm sure they can modify something for you, but it'd probably would cost more, I'm sure.
Why not just hog out the manifold (that's free if you have the tools) and run a catted downpipe/catback?
You'd still see gains there if you haven't done that yet.
The Racekar - SOLD!
2007 Cashmere Metallic Chevy Cobalt LT Sedan
2010 VR Cobalt 2LT Sedan
Debadged, ZZP Intake, Custom 2.5" Exhaust/Borla Pro XS, FE5 Bidnez with KSport Springs.
Previously dumped on BC Xtreme Low's...RIP LOWLYFE :(