skorski,
We feel the same way about the straight piping on a 2004. 5, they just don't sound like the Cummins of old! We do have a MBRP replacement performance muffler that uses the factory pipes and just bolts in. It even uses the factory mounts with welded hangers etc. Uses the same type of muffler in our full systems using a ceramic blanket and stainless steel wool packing materials. It's built from T-409 stainless steel just like the factory system is so it matches for a clean look. You can install it yourself and the cost is basically the same as a replacement muffler built from stainless, very reasonable.
Mark @ DPPI