My fuel gauge in my 99 didn’t work for a while and my pump went out recently and i changed the whole sending unit. The gauge worked for a few days and then it stopped working again i’ve checked the wiring at the plug but not at the top of the unit or in the tank. Could it be the sending unit again? Or something else like the computer. Sometimes the gauge will show a full tank and go down fast and gets to around 1/2 and the low fuel light kicks on and at about 1/8 or so the gauge drops out below E

 

With the parts we get today, who knows?

 

Might be the unit, but check the wiring behind the left tail light. There is a connector in there that famously develops green funk. Jumper out the connector. In there are your pump wires including the ground wire for the pump, if any of those aren't making connection that might do it.
That said, I have had so called brand new pumps with fuel gauge issues too