is your X bodylifted? If so then definitely check your lines. If not then check around your fuel tank by the fuel sender, it is accessed from inside the cab so maybe that's a lead there. Otherwise have you transported any fuel canisters? I know it sounds dumb but that smell can linger for a long time.
ever find the leak?
ouch... if there is raw fuel going through your cats... they will turn cherry red hot and that is no bueno