Maybe it's just me, but MPG isn't exactly a goal in itself. What I care about is the cost per mile. So yes, increasing MPG is good, but if it means that I have to pay 30 cents more per gallon for 91 octane at the pump, the extra MPG isn't worth it. That's not even factoring in how long that extra MPG is going to pay back the cost of the tune itself. Is using the tune + 91 going to improve on maintenance costs and overall life of the vehicle?
I get that a tune is usually about improving the performance of the truck and that makes perfect sense to me. I can see where different tunes maximize performance offroad, DD, towing, etc. I can see why different tunes are different trade-off points between cost and performance.
It does become tough when comparing different tunes and cost per mile.
It's my job to sell honestly, but there is a lot of options out there tuning wise for these trucks.
There is no magic really to an engine's fuel economy (it's combustion efficiency really, doesn't matter if at part throttle or wide open) other than making sure all available fuel and air in the combustion chamber is consumed as efficiently as possible at the right time yielding the most downward force on the piston.
Ford has ignition timing set obviously to be pretty close from the factory, close enough to the point where some people with stock trucks occasionally ping as noted in various threads in the forums here. This leaves very little on the table for tuners to improve unless optimizing for a fuel with greater octane and taking advantage of greater stored energy in the fuel, or placing the engine in a more fuel efficient RPM range.
Although I cannot speak for tunes other than ours, the gains we have experienced in fuel economy have been related to the transmission tuning we have offered as well as very slight tweaks in the engine side of the tune. We tend to keep the engine slightly higher in the RPM band with our shift schedules and tend to shift sequentially in order to avoid lugging thus less load on the engine (less fuel burned), and we play a bit more with torque converter lock up to ensure that it is locked when necessary to reduce parasitic losses.
Also by not performing multi gear up or downshifts, we can stay closer once more to the engines most efficient operating area by not having as wide of a swing in RPM per each gear change.
Maintenance and overall life is a tough thing to estimate as there are so many variables outside of a change in tune that can change the ultimate outcome of useful life.