I have a 2004 2500HD, 6.0l, extended cab/short box.
I would like to try and get a better sound and better performance...hell might as well ask for better milage too while I'm at it.
I don't want to void my warranty....
Is it possible?
If so can you recommend any products, not looking for obnoxiously loud but I think I hear bit of a familiar sound coming from the stock exhaust that reminds me of my old '74 Camaro but it's being pretty well muffled :P

Can I wake up this beast without giving up the warranty?

I have a 2004 1500 5.3 and i too was worried about warranties and aftermarket mods. I put on a k&n intake and a flowmaster 40 series. When i went to the dealership to get something checked out i asked about the mods and they told me that if there is a problem that could be DIRECTLY traced back to your mod, then it voids that part of the warranty. A bunch of people in this forum have posted similar comments about aftermarket mods and voiding warranties. As far as my mods, it finally sounds like a v8 with the intake and exhaust and did notice a very small increase in MPG. So hopefully this helps.