I know our 2003 GV had a stainless steel system. It wasn't the prettiest (stainless steel...not polished stainless steel) thanks to Michigan winters but it was holding up fairly well. All I did was have the stock muffler cut off and a Magnaflow muffler put on.
Unfortunately it was wrecked last month at 52k so I can't state much about it's longevity beyond that.
Perhaps yours is aluminized tubing instead of ss?
I haven't had the time to check over the XL7 to see what it has. The Magnaflow is coming though...
