My car is of similar vintage (98) with a similar problem. After digging in deep at Renntech this is what I discovered:
Our cars have a fuel gauge sending unit that sometimes loosens up out of position or the float simply sinks a little over time. This indicates that the tank is empty when it may actually be 1/4 full. Others have repaired or replaced the gauge sending unit only to have it loosen up or sink again after a few years. I have not fixed mine yet (gauge misreading for four years) because it really doesn't bother me much. I have had many other cars/boats/airplanes with no fuel gauge at all. A fuel gauge that is overly pessimistic is more of a "feature" than a defect in my simple mind. I just have smaller main tank with an extra large reserve.
If I ever need to get into the tank to repair something else I will also deal with the sending unit. For now I can't be bothered. I just pay attention to trip log mileage.