I am a college student and I have a 01 f-250 diesel stock, other than a leveling kit and exhaust. The truck has been in my family and taken care of very well, I have to drive about 80mi a day on the highway and I am looking to up the mileage on it. I know a car seems smarter but I love the powerstroke and need a truck every now and then ( not for any heavy towing) I was thinking of changing out the gearing from the 4.10 to 3.55's, right now im getting about 17 around town and on the highway. What could I expect (mpg and rpm) from the switch? Also what kind of programmers and gear swap kits are going to be the most reliable? I am mechanically inclined and am going to do this myself.