I have a 2006 GMC LBZ 2500HD and i love it so far. The only thing is that it is too quite so i want exhaust. My dad has a 2007 lbz and he put banks 4 inch cat back exhaust on it and it sounds ok, but i want 5 inch turbo back, but he wont let me cause of warrentee. i have been looking online for exhaust systems but dont know what is good. im just looking for a stainless steel 5 nich manderal bent cat-back system, what would be the best for my truck? or is it possible to get a new down pipe and 5 inch into the stock cat then the system out the back? im still kind of a newbie in the diesel world so any help is great thanks.