Q7 can correct me if i am wrong, but the E53 tank holds about 24.6 US gallons of liquid (gasoline), so, at the pump, if you manage to squeeze into the tank 23.6 gallons (hopefully the NY pump is calibrated correctly), you only had about 1 gallon of fuel slushing around... this is what bcred is suggesting... if your MPG is about 15 , then for the 80 miles left on the computer screen, you should have about 4-6 gallons of fuel left in the tank, and if you fill up the tank only 18 gallons to full, then you have those 4-6 gallons for real... if you pump 24 gallons, while your computer is reading 80 miles to empty, then your level sensors are lying to you...

there is only one live pump and the other one is a siphoning pump, does not have electrical parts in it... the pump with electrical motor is on the right side of the car, that is the one that sends the fuel through the fuel filter to the engine... the passive siphoning pump sends the fuel from the left part of the saddle tank to the right side... sometimes, if the left side has fuel, that side will register decent amount of fuel but the pump can't siphon it because of debris, or other issues - thus you have a reading of fuel but no fuel gone to the active pump to go to the engine... therefore, if you do what Q7 suggested, you can see the amount of the fuel in left tank, and if that is the amount that is reported to the computer but not picked up by the pumps...

a little bit of homework will help you narrow down the issue and avoid unneeded expenses...