How's your evap system? Do you have one at all? If the tank isn't venting properly, it might be causing a partial vacuum to form and that will force the pump to work harder. If you've still got the canister, try disconnecting it. If you've had the canisterectomy, blow down the vent line with compressed air (from the tank vent in the filler neck assembly).
If you're all about the destination, take a fucking flight. - Frank Turner
Got brap, and twice as much fuel as you. - Akarob