If you are not wanting to switch anything back for emission testing then your one option would be to unplug your EGR valve (1-2mpg gain).
You will have a CEL on, but you can buy a tuner thats capable of delting (Smarty, H&S mini maxx, XRT) that will disable the EGR and turn off the CEL.
Another option is to go with EFI-Live. You can unplug your EGR valve and get a custom mileage tune for your truck that should help increase your fuel economy.
Aside from that the only other thing that comes to mind would be going with free-spin hubs up front. People claim 1-2mpg increase, but it comes at a price. Those are things you can do that wont require tools or time to convert back in order to pass emissions.
The standard deletes will net you a little better fuel economy (EGR, EGR cooler, DPF, NOX, CAT) but those require swapping parts back and forth.
Oh another thing to look into is a TS MP-8. I am getting ready to sell mine here soon because I will probably need custom tuning before long.
Hope this helps and if you have more questions post them up.