03 2500HD engine & exhaust mods

Just traded a 98 7.4 for a 03 2500HD 4x4, because I don't tow much any more, hope Im not going to be disappointed. My question is has anybody had any experience with Vara-Ram products, the VR velocity stack, and VR king cobra ram air and cold air induction system. Visited with a guy with a velocitystack, he is very happy with increased mileage and HP, for a cost of $50. Next he's trying the king cobra. VR guarantee's its products performance or will buy it back, so they say. Also he put on a set of Gibson headers on his 8.1 with stock exhaust and was impressed with mileage , HP, and torque increase. He then replaced the rest of the exhaust system and was not impressed, he noticed torque decreased, probably from to little back pressure. He stated to me Chevy's problem has aways been can't get the exhaust out of the heads fast enough. His advice was headers with stock exhaust. We are at 3150' elevation in Montana and he stated we can't get enough air into the system to create the problem of exhaust not getting out of the restrictive OEM muffler. I wanted to change to a Pro-Flow 2500 muffler, he said I was starting at the wrong end. Has anyone had any experiences with intake and exhaust mods on a 03 6.0?

2002HD 8.1, crew cab, long box 58,000 mi all stock equip.

You might want to post again to get attention.

I have been looking at the k&n intake system. Results depend on who you talk to.

Curious to see if anyone has used the vr system. It sounds like it might be worth it.

Looking to squeeze all the mpg and hp i can with bolt on mods. Keep this updated