Fact of the matter
The fact of the matter is there really isn't anything that will boost your mileage significantly with a truck that weights 6000 lbs. and has a huge 6.2 V8. There are few things that you can do cost wise that will have any real return on your money! Performance yes gas millage no. Figure a tuner at $500 bucks and CAI at $200 bucks with maybe a mile or mile and a half improvement how many miles and how long do you have to drive to even break even on your investment. Not to mention the risk of a tuner voiding your warranty. Remember you can definitely increase performance but with that comes the risk of a heavier foot and there goes the gas mileage.