Welcome!
Some useful places to go while you're still new:
http://ecomodder.com/forum/showthrea...-mpg-5170.html
http://ecomodder.com/forum/showthrea...ower-6341.html
http://ecomodder.com/forum/showthrea...ehicle-83.html
Seein's how you're trying to wring better numbers from a full-size 4x4, you've got an uphill climb, but looked at another way, a gain of 1.0 MPG represents a much larger percentage boost for you than, for instance, me.
Start a garage page for your truck, it helps with keeping track of how the various mods perform. Tell us more about it so we have a better idea both of the truck's "mission profile" and what kind of options are on - and off - the table.
Jump in, the water's fine.