I had this problem on a 98 gt when they replaced my fuel pump. there is a pipe that goes into the tank from where where you put the gas into the tank to the actual tank. There is a rubber gasket there they did not have the part in stock so they tried to reuse the old one. When I filled up my tank up past the line going into the tank it leaked all over. Once it fell below the line it was ok. I had to get a new gasket installed and it fixed the problem. I would not drive the car if its still leaking .