i know this is chevy area but i was just askin for an exhaust question since not to many look over in the dodge cummins area just an exhaust setup for any diesel

dieseltruckresource.com has a huge 3rd gen cummind section.

The 06' cummins has 4" turbo back stock. The best thing to do there is delete the muffler and run strait 4" pipe. It will still be pretty quiet without a muffler in the cab, and EGT's will drop quite a bit, especially while towing.