I had a problem like that when I installed a 255 intank pump with a new fuel filter. The gauge will go past max when I get on it or after a constant loong cruise (3hr trip to Houston averaging 80-90mph). Turned out the Autozone brand filter was defective and I replaced it with a Ford unit and that was the end of the gauge problems and the smell of gas as well.
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Black SN95
TFS heads, Holley intake, AFM B-2 cam,
12.9 @110mph best ET
13.06 @111mph best MPH After gutting out clogged cats and a much better tune. Took Nitrous out for warranty work

didn't have time to put back in for track.