All 6.0 have a VGT. It is a matter of what year the truck is to how man vane there are. The 03 has 7 vanes, 04 has 11, and the 05s, and 06s have 13. That is why the 03 has more of a whistle.
I have the MBRp turboback duals, no cat. As for the muffler, it might as well be straight piped...