Sounds to me like someone is bulls---ing you or at least not telling you the whole truth. There are not 2 fuel pumps on your car.There is only one and it is on the right hand side of the tank. The "thing" that delivers fuel from the right saddle is called an "ejector" and it works because the pump puts a negative pressure at the ejector and that causes fuel to be delivered to the windage tray that the pump sits in on the right hand saddle.So in effect what happens is that the left saddle is emptied first and then fuel is picked up thru the right saddle until the tank is empty.The most common problem is that the ejector plugs up and fuel cannot be sucked into the right side,so the right empties and you still have six or so gallons on the left that you cannot use,still being displayed on the gauge as about half full.(There 2 sending units and by using an algorithm the microprocessor in the instrument cluster is able to make the gauge and trip computer work)