Something is still off. Even with the larger tires, you would be going 9% more miles, which means approx 9% more fuel milage which is less than 1 mpg.

You have something else wrong

 

If you're running app. 35's with stock gears your fuel will be lower than with stock tires. Got an axle code?

Upload pics by clicking the and entering your pictures URL into the space provided. should pop right up if you do it right.

 

Its a standard with 4:10 gears front and rear

 

https://www.ford-trucks.com/forums/p...ctureid=122179

 

I would say NO bumper will at least take 1 mpg away

 

yeah,no bumper and incorrectly set odo,large aggressive tires and you take a sucky 9-10 mpg truck and get a more sucky 6 mpg truck all easy.some don't even get 10 mpg setup as stock,so no surprises here.

 

Yeah, first thing would do is change the bad pump, then check the fuel crossover valve. I have a 94 f350 crew cab, 460 with a full banks kit, zf5, 4.10 gears, 285/75/16 tires. Driving like a sane individual, it gets 10 mpg city. On the 3100 mile ride home from california, it got 12.5-13 mpg at 65 mph. A jump to 70-72mpg brought it down to 9.5-10.5 mpg.