lets keep it simple, send me your bin and a datalog and let us have a look at what you're working with. dont even look at that narrowband o2 gauge. it's useless.

got to teh gas station only to realize my gas tank filler neck was actually hot to the touch. and exxtreme pressure buildup. although i dont have any sort of evap hooked up yet.
the evap isnt hooked up? ... what about the external vent that runs down near your diff? if it's there, it'll be fine. these f-body tanks and evap systems are designed to build up a couple pounds of pressure. nothing should make the filler neck hot, really. that could be a lack of heat shielding between the exhaust and the tank which should be resolved immediately. the fuel in the tank can get a bit warm from recirculating heat soak from the rails, though.