From OP in post #5,
"This mod was based on adding 50% more air and changing shift points in the trans and RPM limits."
How do you get 50% more air without a supercharger or a turbocharger? The bore and stroke haven't changed, so how much volume could the air change without some help?
Ram air, at 100 mph is less than 3/4 psi, which isn't going to help much, and if you did get 50% more air, you would need about 50% more fuel, else you would be very lean and burn valves and pistons. I agree with others, do a hand calculation of your mileage, only way to prove one of us wrong.
Also, Cummins is a diesel, whole nother ballgame than the 5.4L. You can control turbo boost pressure on a diesel and get more air, and power.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT