l had this car brought in jan 2003 but l have a failing fuel pump problem which has reduced my pick up and mileage of my car. does anyone have a similar problem?

Undo the pipes from the back of the pump (the ones that go to the injectors) and get someone to try and start it. If diesel is comming out, it is probably not your pump.

Could be injectors, mass air flow meter, air in the fuel, water in the fuel.

It could be the pump but l doubt it somehow

Buy a new pump...

Any defective pump will not supply the necessary fuel as per the engine load but has nothing to do with mileage.

Keeping the fuel tank less than a quarter is harmful for any fuel pump due that the fuel works as lubricant and cooler for the pump.

If O2 sensor is damaged is other cause of extra fuel consumption.

Have you ever check the fuel, air filters and cleaning injectors, change spark plugs etc, for pick up improvement?

UMMMMMMM.
take it to the machanic you just need to losen the plugs.