92 should be fuel injected

Very unlikely it would vapor lock, how about a fuel pump going bad instead

I have built driven wrecked and wheeled xjs for years, never saw a fuel injected xj vapor lock,

Vaopr locking usually is in the carbs of a non efi vehicle, you should not have pressure in your tank though, is your charcoal canister clogged?

There is a vapor collection system on the older xjs. It is supposed to collect excess vapors and is part of the vent system to the tank. Not sure of its origin or usefulness, whne they clog up the do not vent properly, if i recall mine was on the firewall on the drivers side