My spillage history is as follows:
Bought  90GL in 4/97  No fill up problems.  About last summer, I started
with the post-fillup smell.  Replaced crossover pipe, grommets, hoses a la
Wilfy kit.  Smell went away, but a couple tanks of gas later the filler pipe
belching started.  My van has the later ball in the bottom of the filler
neck, so my next course of action will be to replace the valves in the top
of the expansion tanks under the front fender wells.  Something in these
systems isn't breathing properly and is not allowing the escaping air(that's
being replaced by the pumped in fuel) to reach the atmosphere, right?  Maybe
it could be a blockage or constriction in the ball valve assembly at the
bottom of the filler neck piece.  All I can say, is that the 2WD models
didn't do it when they were new, so there has to be something that has
failed somewhere.