I just tracked down an exhaust leak that was covering my engine compartment with black soot. To examine the exhaust piping, turbo connections and exhaust manifolds I had to remove the heat blankets. Once removed, the leak was apparent as the heat had burned the inside of the blanket and was easy to trace. For other diesel owners with Cat or Cummins engines the original supplier of these is Advanced Thermal Products (ATP) http://www.atpwrap.com/ and they still make replacements. You can buy the whole set(s) or just a replacement piece. Hope this is helpful to others.
Tom

Exhaust Leak, Part 2:
For those with Cat 3208T Diesel engines: If you see black soot in the engine compartment and follow the trail above, you might also inspect the blankets covering what CAT calls the risers - the two pipes from the exhaust manifolds to the inlets of the turbo. They are short pieces of pipe with an accordion bellows and after some time they will crack around the bellows part. This can be confirmed by looking at the inside of the blankets that were removed - if there is a burned area into the blanket that will be the location of the crack. The good news is they are easy to replace from the under bed trap door. The bad news is they cost almost $300 each! There is not much option so consider that when you look at a 3208T engined unit. It will cost about $1,000 for a shop to do this. Hope this helps.