First thing first change the fuel filter! 50% of the trucks i see with your problem have never had the fuel filter changed. Its quik and easy, i would buy a gm filter but thats just me. Any mods( air intake, exhast,or larger tires) If this helps but does not meet your liking of the amount of power add an edge juice with an attuide and then you will have no problems spinning your tires. But make sure the truck has new filters all the way around and check all hte fluids.I just picked up a 2005 sierra 2500 with 44,000 miles on it. Love the truck but feel like its doggy off the line. Will not spin the tires and in the upper rpm's it feels like it cuts out alittle. Any ideas?