||Thanks, i'll try this!
The car has the charcoal canister system deleted, and the fuel tank vent line is open to atmosphere in the engine bay. That being said, the tank does hiss as though it's relieving pressure when i go to refuel it and the level is near empty (regardless of the temperature of the tank).
I was under the impression that heating the fuel would cause pressure in the tank to go up, which would increase the boiling temperature of the gas. I guess the point is also fair that drawing fuel off faster than fuel vapor can fill the emptied volume would cause a vacuum in the tank, which would lower the boiling temperature of the fuel.