No mods to the truck that should increase milage, except the chrome plated tailpipe extension. I fugure it's good for 2-3 MPG.
Actually, most of my driving is between home and Denver Intl Airport, which is about 20 miles each way, almost all freeway driving. I ordered the travel package with the overhead computer, and monitor it alot to judge fuel comsumption. I have been driving consertivily, trying to maximise the economy, like taking the truck out of gear and coasting at freeway off ramps, etc. It seems to help. I also use fuel additive (Power something from WalMart) and get all of my diesel from Flying J.