Check the rubber seal where the gas filler neck goes into the tank, does it have any cracks/leaks there?
1990 Oxford White GT(The White Elephant) Maximum Motorsports subframes & c/c plates , Mac O/R H pipe, Flowmaster "Delta Flow" mufflers, 3.73's & Mac girdle, A/C, EGR, & Smog deleted, "B" Springs, chrome Pony R's 17x8, 17x10 daily driver!
2003 SVT Cobra, Redfire Metallic
JLT RamAir Intake, Billetflow 2.93 pulley+ idlers, Mac Pro-Chamber O/R mid-pipe, Nitto 315 dr's,Billetflow brace,weight reduction, Tuned by Amazon T.S. w/ SCT software- 451rwhp/457tq