I was under my truck (02' 2500 4x4 6.0L) and noticed either a crimp or dent right at the curve next to the spare tire. It looks like a dent but I called a local Chevy service rep and he said it's factory to keep the spare from melting and needed exhaust back pressure. Any advice? I bought the truck used and never noticed it before. The exhaust is 3 1/2". Thanks!