When I had my 500 SEC I removed the rear muff and had a straight pipe made for that section. It made it rumble just a little. Perfect. When it came time to sell, I put the stock muff back on. I've also done this with other benzes with good results. The 91 350sdl, my 91 300d, maybe others I can't remember.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.