[ckaram]

I wouldn't worry about "warranty" for your mufflers. That's what the axleback is...a pair of mufflers.

FWIW, I purchased a pair of GMPP muffs from a user off this site and had them installed on my SS by a muffler shop. Just yesterday I was at a dealer for my first oil change and they complemented the mufflers on the car when it was in the air. I wouldn't worry about it but it's your car...