Pawned, look up metermatch, I had the same issue with my gas gauge and this pretty much solved it. This is a device that will calibrate your sending unit to your gauge even if they are missed matched.
I have had one for a few years now. I have set it up at least 3 times and it never has worked once I took it off "program".
like I said, not that I redid the wiring and grounding to the gauge and the gauge is valid, I will attempt the MeterMatch again.