I agree that you should check the ground. My Camaro however does the same thing when it is full of gas. The needle probably goes about an inch past the "F." It stays there for a bit of driving, but then starts coming down. I never really worried about it myself. When I took out my tank and did some work and reinstalled I did notice that the problem was worse and the needle was pointing WAY too far past full... to the point that it was pointing straight to the right. I cleaned up the ground contact a little and the problem went back to normal, an inch past the F at full.