AND, , , , ,Check that fuel cap to see if you get a "whooosh" sound when you loosen the cap. A 20 yr old cap will sometimes prevent a proper vent of the gas tank causing a high pressure imbalance to the outside pressure. You can soak the cap in seafoam or a vinegar/water (50/50) solution for a few hours and blow it clean with a few blasts of air.
Hello and Welcome . Another possible source of the problem could be the vacuum fuel cut off valve is failing. The vacuum hose could be leaking/loosing vacuum to open the valve or the diaphragm could be failing and not opening valve.