A drop in air filter or good CAI. Depending on where you drive, tires make a big difference in mileage. The off road style tires weigh more and tend to drop MPG a good bit. So if you could go more for the street truck tire the better the MPG's you'll see too.
i put an open air breather on it this weekend and ajusted my shift points in the trans and there is a noticeable diferance in it already watching the mpg's to see if it makes a differance. i useually do try to keep my foot off the peddle as much as i can but every now and then give it a little extra just to have fun. is there any parts that i can upgrade or changethat would help me move in the right direction
Has your truck got a cold air induction yet? I have a tight budget and did a drop in but will get a good CAI and open the exhaust. The tuner is the last mod I'll add. The best mod is a light foot on the go peddle.