Alright,
my tow rig is a 99 Chevy C3500 2wd SRW with @ 40,000 miles on it. I love the truck, it's been flawless for me. It has the 5.7 and the 4L80E tranny. It already has free-flow exhaust and a K&N. I'm looking for input on what is the next best mod to do to get more torque for towing out of the 350. Is there a good tuner out there or chip that somone has used and can personally recommend. There's plenty of stuff in Summit, Jeg's, etc.. but I'm looking for anyone with feedback. Also, the drivetrain is still under warranty so I'd like to get something that is plug and play so I can remove it for any warranty work. I figure I should be able to turn the 350 up quite a bit without doing anything to the tranny (4L80E). Any help would be appreciated.
K

You can get a few more horses with a chip it is just a matter of deciding which one you want because there are so many different ones.. Which one to go with will depend on what your trying to spend.. Super Chip and Hypertech seem to be among the most popular.. Hypertech sells a programmer that you can adjust manually to suit your needs instead of a preprogrammed chip.. Either will work it's more of a personal thing..

A good set of headers will help too but I don't know if that will void your warranty.. Some people have no trouble with their dealer and others say they did so it's best to ask yours 1st..

www.fullsizechevy.com there are some custom programers on there that make some kick ass chips.

I went through this recently. I have a 97 C2500 with a 4l80E and Vortec 350, there just isn't a big aftermarket for those motors(with the stock fuel injection setup). Short of port work in the heads and a camshaft, headers, a chip, and what you already have are all there is to do. But even the Doug Thorley headers, they themselves only claim a 5HP increase in power. Seeing as most companies overshoot what they actually make, I'm not spending the money on them.

We have sold this programmer many times its a vary reliable file.
CK Pickup 5.7 . 1998-2000 PN 2265 / +21HP/+34ft/lb
Mainly all of the computer work is done in the shift timing of the solenoids inside the 4L80E. Some light work is done to the fuel and timing maps of the computer program. Keep in mind if the engine is too lean the HP is much higher but the fuel-cool compensation ratios are wrong, next stop thermal meltdown. This would be the last and only mod, I would recommend. If the truck runs great, don’t change anything.