quicksilverGTO

On my 2004 GTO, I've been noticing that one tailpipe has much less carbon buildup than the other. The other one is so blackened that specs of soot accumulate on the bumper. I haven't thrown any codes, but something just seems wrong with one "clean" exhaust pipe, and the other one considerably "dirty." I have a RWTD tune and checked the 02 reading and fuel trims for both banks and everything seems to be fine, with the #'s for both banks coming up nearly identical at different engine speeds and under different throttle loads. Should I be worried about anything? Or do I not have a problem at all?

-Mike