gimmie

My gas guage goes down to empty and the gas light comes on all the time. Once I go below 1/2 a tank it happens much less often. When I fill up it will come on after less than a mile of travel and stay on for 30 mile or so(Didn't happen this bad until dealer fix ?). It seems to go off when I stop or slowly go up steep hills. It's still under warrranty and has been to Ford twice so far and is due in this Friday for the third time. The first time was inconclusive and they said I put in too much gas which I never do(never one cent over after the full click on the pump). The second time they replaced some sending unitassemblys(7r3z 9a299 c and 7r3z c9275 z c). That seemed to have made it worse or the existing problem is geting worse but the light seems to stay on more and more every day until I get under 1/2 a tank where it still comes on much less often. Anyone out there know more than Ford's Computers ???