S350D exhaust question

[I have arrived]

I have a 1994 S350D and need to replace a part of the exhaust. I am trying to order the part on line but am not sure of the part number. The catalogue's list only 2 parts - "Front" or "Back" muffler. I can use process of elimination and deduct that the rear muffler is not the one I need because that piece appears to be in good condition. It is the pipe directly prior to the rear muffler I need (where the cat converter should be). Does a diesel have a cat?

Anybody have a schmatic or drawing that would help in identifing the part # I am looking for. The parts on these 140's are pricey - I would like to avoid ordering incorrectly.