The only 'tuner' a 6.7 Ford
needs for better mileage is an egg. That egg needs to be carefully positioned under the right foot.
My '11 6.7 is Ford's JOB 1. This means that it started out at less then 400/800 Hp and torque and was 'tuned' by Ford to that 400/800. That JOB 1 also means that there is the possibility that eventually one of the RH head valves may break and destroy the engine. I still have a Ford ESP just in case up to 2020 and 136,000 miles. It currently has 110,000 miles, ~75% towing something pretty big with nothing more then a few JOB 1 birthing pains in the first 15,000 miles, all corrected under warranty. Since then only a plastic CAC tube, replaced last year with a steel version.
With that said, and with summer blend, non-bio fuel, my empty fuel mileage ranges between 19-22mpg. Towing, 10-13, all dependent on the diesel fuel's cetane rating and make up is as well as whether I scrambled that mythical egg under my right foot. If I 'deleted and tuned' my truck for something well North of $2000 (lots of fuel's worth) I
might pick up a couple miles/gallon - but maybe not. I also couldn't trade it in at a Ford dealer.
Your truck, your dollars, your warranty, your decision for not a lot of gain
