On a recent trip driving my 2000 mroadster ,6500 miles,I filled up at the gas station and then a few miles down the road the gas gauge went to empty and the fuel light came on.It would be a mile or two later and it would go back to full then drop again soon after that.After the car ran for about 20 or 30 miles the gauge was normal,only under full conditions did it act funny.I never top off the tank,once the pump clicks off that is all I put in.Has anyone else had this problem? And what may the solution be? Thank you.