Fuel filler neck.After consulting with Filler Neck Supply in Washington state.
You DO NOT have to remove bed to replace fuel filler neck,looking under rear fender,IT'S RIGHT THERE.Easy replacement.Couple hose clamps,3 screws out side,and done.This is on my 06.Plus Filler Neck Supply is 1/2 cheaper for the neck
that i've found in town.
But if your hose to gas tank is shot,you may have to remove bed!!
see ya,old retired guy