I am gonna go with the bulets aren't resonating enough. I didn't look up to the front of the truck, but what 1slow says above would help as well...x-pipe maybe. I forgot what you said...no matter, I don't think the bullets are cutting it.

 

I have x-pipe,no cats, and x-pipe DI/DO magnaflow muffler and I also get the popping sound at full throttle.I think I am going to go with the flowtech warlocks with built in cutouts to see if that quiets it any.

 

If you give me a couple of weeks, I'll have a sound clip for ya from my radixed 6.0 w/ 3" LTs and dual 3" flowmaster 50s, no x pipe, no cats. It should sound similar to how your's would, it has a GT2-3 cam and will have 6psi when I first put it in. The dual 3" 50s were still pretty loud on my whippled 355, but no rasp at all.