This sounds more like a fuel sender problem. There are two sender units, main and sub, one on each side, accessible beneath the rear seat. The main sender is attached to the fuel pump on the right side. The sub sender is on the left. I can't tell you what the difference is, but my guess would be that the actual fuel gauge reading is some kind of average of the levels sent by the two sensors. If one sender unit goes bad, you would see erratic reads like you're experiencing. The good news is you probably only have one bad sender, but the bad news is that you don't know which one.