What most do is to add a vent. Take the fuel filler neck and put a nipple on it with a vent hose so it won't back up on you. I'm sure there are threads on this here somewhere, that's how I found out about it!
I'm having a smiler problem but not to much filling up I replaced the charcoal canister but still have the pressure build up. Could be a blocked line. I'm going to start there with the line to the canister first. Mine is all original factory 1987 :dontknow:
that metal linen on the drivers side that comes off the frame and into the canister is the problem, its either blocked somewhere between there and the tank, or in the tank. take an air blower and put a little pressure back on the line from where the line comes off the frame to the back towards the tank. it could be a simple blockage. if it flows freely, suspect the blockage somehwhere after towards the charcoal canister. when people remove it they seem to like to put a rubber plug over that line since its the only vent on a 5th gen tank, it will build pressure.