I have to disagree on the ethanol theory being the problem in this case, ALL of our station have ethanol in it & my car doesn't starve for gas at all, what it does do is after running a good 10-15 minutes around town is the pressure on my gauge will start flucuating (drifting) around, but then it'll return, is it the GAS, IDK, but even under these situations it'll run out fine under WOT through all gears.

I think his pump is either "sucking air" somewhere or theres a restriction, OR the pump rod is mushroomed because he mentioned he never took it out & looked (unless i missed something).

Another thing i thought of & it happened to me is, the short rubber hose that goes from the tank sending unit too the hardline was kinked, had another car that the hose was so soft the suction from the mech. pump was making it callapse. These are things to check. I'll bet anything "once" you find the problem its going to end up being something you over-looked & simple.

Its not rocket sience, you have a clear path for fluid to flow through, then you have a pump that sucks & pushes the fluid, pretty simple really.

Check the hard line & let us know what you find.

1 more thing, did you ever try running it without the gas cap on???