I just purchased a 2003 Chevy with a 6.0 2500 hd 2wd.....anybody done any exhaust work or other mods that will help in letting her breath a little better? and also how do I tell what gear ratio I have?

Look for GT4 or GT5 on the build sheet in the glovebox.

GT4 is 3.73
GT5 is 4.10
G80 is Limited Slip

Don't expect much gain from that engine. You might get 30HP or so total with a cold air intake, free flowing exhaust, and a powertuner like Diablo Predator.

Contact www.pcmforless.com Best $250 you'll spend on that truck I bet. From there, long tube headers and cold air intake. Next step would be a turbo. Unfortunately , the transmission makes the 6.0 feel like a dog. But you'll have a hard time killing it at least...

Sorry sydways, but handheld programmers are junk and those engines are packed with potential. Yes, you need CAI and exhaust. Take it a step further with thermostat, long tubes, shift kit, e-fan, or a cam. Or any combo of those. The KEY to waking those engines up is a custom tune from westers, PCMforless, wait4me, etc. to match your mods with the correct timing and a/f and desired amt of TM. The handhelds do nothing for torque managment. Do yourself a favor and buy the CAI, long tubes, catback, and thermostat. Send your computer in or buy a core, and have them work it for you. I did the cat back, CIA, and shift kit on my 6.0 HO out of a Silverado SS and it flat hauls with the PCMforless tune.....you will be suprised how hard they pull as the RPM's increase when you dial down the TM. You have the 4L80E trans so your set with good stuff there. You truck will haul balls. With just a tune alone they are supposed to get 60hp out of the LQ4 you have.

The 4L80 trans is a great trans, the only thing is it has a high first gear ratio. It does make it feel like a pig. I have the same setup in my 07. Where can I get the headers you guys mentioned.

Check out fullsizeforums.com or something like that. There are several companies that make long tubes. One out of TX, but I cannot think of the name. Just make sure you get your PCM tuned for em'

I am more concerned with economy so if I can pick up some mileage by making it breath easier that would be great.....I have been driving a 4.7 dakota for about 3 years....so th e stock 6.0 more than suits my needs on power but with fuel these days was wondering if anyone had any input on mileage gains........but you can never go wrong with more power..

Do some homework on your tire size and style, I lost about 2 MPG going up from the stock size (Yes there is 3-5% error in the speedo now but I am still down), back then fuel was $2.60 at its peak. My next set may be the 245's again. The biggest variable is the driver, if you want good mileage do not drive it as if it is stolen, and get used to being passed.

Order/send the PCM out. You're probably getting 12/16mpg? If the tune gets you just 10% better mileage, it will pay for itself in a few months depending how many miles you drive. Tell them you want a mileage tune, not so much for power. And then it will be up to you to keep your foot out of it. cold air and long tubes won't improve daily driver mileage. Less throttle, shorter shifts, and reducing parasitic drag will. Air in the tires, best fluids, brake service are things to consider.

I just mounted and programmed an Edge in my neighbors 2008 6.0 and his fuel consumption got 30% better while towing his camper. Easy to do and very informative info out of that little box.