Sounds to me that the FPR was not the real problem and that the one of the pumps is the problem. Are you sure both the in-tank pump and the external pump are working? You can verify by looking under the car while it's running and listening/feeling the external pump. You should also hear it hum if you turn the key to Pos II and pause there before starting. Note you have to wait 5 minutes after the car has been previously running or the pump won't do this when you re-start the engine. You can also remove the gas cap and hear the in-tank pump run while the car is running. The fact that the engine ran better after you filled it up is a classic sign of a bad in-tank pump.