What kind of milage does it get now? I would think a good tune up and maybe something like a K&N air filter would help. Synthetic oil also frees up some HP (Dan just put Royal Purple in his Dodge truck and picked up something like a mile per gallon.) Air pressure sure helps as well as your personal driving habits...don't floor it but act as if you have an egg under your foot. Keep the windows closed and open up your tailgate at highway speeds. You would be surprised how much drag a closed tailgate causes.

Don