This car has been to Toyota Dealership 3 times. Replaced fuel level sending unit. Didn't correct problem. Put another unit on. Didn't solve problem. Took instrument panel out and "loosened" or "lubed" the gauge. Still not working properly. Level will drop quickly. Then when I get back in the car and restart it will be back up closer to where it was to begin with. Any suggestions? Could it be corrected by replacing the gas tank? Thanks!