Ok my dad has a 05 4 door 5.3L half ton and he was asking me about putting headers on his truck. But he has a warrenty I think its 100,000 miles or so. This is also his tow vehicle for his race car so. Do they have any free mods like for the F-bodys? Thanks if you can help.

Oh I seen a bone stock 4 door the same year and motor like his at the track and he ran a 15.77 spinning the tires. Is that pretty good for a 4 door?

 

You might look at Dynatech's long tube headers and Y-pipe with cats setup. These along with a pcm tune or tuner would help towing out a bit.

 

go to ebay and search for the CAI. i just installed one on my brothers 2003 5.3L. its very nice , quality and perforamce. i would have gotten one instead of my K and N if i knew about it months ago. cut the mufflers off and replace with straight pipe and x pipe. very cost effective.
drop the spare tire
just doing those mods wont void your warrenty at all and should pick you up at the most .2 - .3 of a second

also, give a tune by mail vendor a call and get a performance tune for it. its not free, but its definaly worth the $$. just keep the orginal one and replace whenever going in for warrenty work. good luck and have fun.