Muffler upgrade to V6
 

I want to upgrade my mufflers to get a little more sporty sound out of it, but not a window-rattling sound. GM want $1800 for a cat-back system that gives a slight increase in the rumble, but not $1800 worth. When I mentioned to the service people about other options I was warned about "back-pressure" problems that may affect the warranty. I have looked at several from the $100 glaspak at O'Reily's to the $500 Borla and similar ones. I would like to hear from some experts about their advice on this. Is back-pressure a problem or not? Would it really affect my warranty? Thanks for your help.

Installing aftermarket mufflers will absolutely NOT void your warranty. To deny a warranty claim a dealer must prove that the parts in installed directly led to the failure in question. A set of axle-back mufflers just ain't gonna do that.

That said, I'd go with the Borla axle-back kit.

Borla 11776 Stainless Steel Rear Section | AJUSA.COM