Basically all programmers and chips will give you a great deal of increased fuel mileage as will doing an exhaust system on your OBS.
Chips work much better on the 7.3 PSD than what programmers do. Chips being the actual chip that that goes into the PCM and it controlled by a flip dial you install in your dash or where desired. DP tuner, TS performance and tony Wildman are basically the top tuners on the market. I myself only run DP tuner, but we are dealers for DP and TS performance.
We can certainly put together a nice package with intake, exhaust and Chip for rather inexpensive for your truck.
We also stock superchips, Hypertech, Edge products and SCT for your hand held programmers.
If you want to just do a hand held I would suggest the Edge Evolution. You can typically expect gains of 2-4 MPG depending on your setup and how you drive.
If you have any questions of if I can help PM me.
Thanks
Shawn