OP. I don't know about sound improvements with regards to swapping out the factory headers with shorty's . But from a performance standpoint, the factory headers are pretty good. If you are looking for decent power gains, go to long tubes. And if your car is relatively stock even long tube headers wont get you a lot of extra power.
IMO. the factory system is good.Should you be considering extensive modifications, then by all means get long tubes. But I think personally that shorty headers are a waste of money. Sure, the companies selling them will brag them up, and insinuate substantial power gains. But again, IMO if you want to go to the trouble of swapping out manifolds, go all the way, to long tubes.
2011 GT. Grabber Blue. Procharged. 3:73 manual.Billit LCA's. Corsa Extremes. GT 500 wheels. Racemaster DR's. T-56 Tremec. Dynotech DS . Centerforce DF. American Racing headers/high flow cats 560 rwhp.Donny Walsh tuned
2012 Pony Package. Race Red.3:31 automatic.BBK longtubes and catted X.FRPP Sport axlebacks. BBK throttle body. Dynotech DS. Brembo wheels and tires. Strut tower brace. Airraid CAI. Bama tuned.