2000 grand prix noisy fuel pump?

I bought a 2000 grand prix and the fuel pump is making a high pitch noise when the fuel level was really low during test drive. The seller said it was because of the low fuel and would go away. After adding about 10 gallons it did not stop. I purchased the car and the next morning the noise had stopped. The following morning the noise is back. The seller is a Kia mech. and said he checked the fuel pressure and it was correct. Could this be a fuel filter getting clogged or is it more likely the pump is going bad and needs to be replaced?

The 2000 GTP has a two speed pump, so you you may be hearing the "noisy" pump when it is in high speed mode. It usually goes into high speed mode when the car is initially started and for high boost/ high throttle. Unless you have a drivability issue, stalling, lack of power, random missfire, I would not worry about it.