I've put a K&N Filtercharger and Jacobs Pro Street ignition on my 1995 4.9L. I ran through a full tank on my front and half a tank on my rear that time, so it was kind of hard to tell what it was doing with my milage.

With the second set of tanks (front and rear), I went to 89 octane instead of the usual 87 (that's what the book recommended, so that's what i've been running). Solely with reading my guages, it looks like i got about 18 mpg with mostly in-town driving on that front tank, but on my rear tank it looks like i'm doing about 10 mpg.

I realize that it's hard to tell just from this, but any ideas what's goin on? should I be looking at the fuel pump(s)?

I've also been experiencing intermitant slight hesitation, bogging at low speeds (20-35) while cruising and during acceleration (if you put your foot into it, it seems to clear up). I'm figuring that's a fuel filter.

 

With that much of a "visual" difference between the tanks,either the back tank is pumping fuel into the front tank,or the return fuel is being dumped into the front tank,or,your gauge isn't accurate.If you have been following this board for any time,you will have read about all 3 symptoms I have suggested!The only way to verify fuel mileage is to begin with 2 full tanks,drive a minimum of 250 miles per tank,then refill both taking note of the gallons put back in each tank and dividing the gallons into the miles travelled.You only need to have a functioning odometer to get fuel consumption rates.
Phillip

 

Right before I bought my 93 f-150 Ford put out a recall on fuel taken from a tank and ran through the engine and filling the other tank. I would think that by 1995 Ford fixed this problem, do you notice while driving, if you switch to either tank, does it seem "fuller" than it was? That might be your problem.