I can attest that the regulator/filter assembly does get very hot in the summer after driving a bunch.No, doubt the spring is in the fuel but it is in the body and the hot fuel will will transfer that heat to all the metal. I would think the whole reg becomes the same temp as the fuel most of the time, but once the housing heats up, then it may keep things hot even if the fuel was to cool.
I think so too, but for the life of me can't figure out how or what. It is what made me think of the regulator. If something caused high vacuum that might prevent oil going down the drains. We know you can draw it up the drains if you apply enough vacuum. We have both been there done that. LMAOI would think the oil in one intake to be troubling, or a sign, but it's not enough to go on.
That would be pretty hard with the volume of air that flows thru those air tubes. Might happen after the car is shut off but then it would be in both tubes not one.I think the oil in the tube is just condensation from oil vapor in plenum.
You could be right and I have two or even three issues going on (fuel sender or cluster problem).Can you do a fuel pressure and flow test at WOT in a high gear?
Both your symptoms are consistent of a failing fuel pump.