I have a 88 F-150 with dual tanks, 4.9 EFI. The problem is the rear tank will show that it is full when it is, but once it gets to about half a tank, the needle will dance from full to empty. When it gets to about 1/4 of a tank, it falls to empty and stays there. Wasn't all that big of a problem, but then the front tank started doing the same thing. So now, once below 1/2 a tank of gas, I never really know how much I have. I have in fact run out of gas on occasions, but have gotten smart and carry a gas can with a couple gallons in it in the bed of the truck.
Any ideas??