"I might mention that the car has a heavy turbo duty radiator and uses no fluids of any kind."

Ok, I am going to be the "one to bite" on your last line of the post. (: o)
I hope you meant, it does not leak any fluids as radiators need something in them to work! (:-)

It appears to me you are pretty sure its a gas issue from what you are saying. It acts out of gas or was limping home on a ECU/AMM which can feel like the same thing.

Have you considered a vapor lock condition?
Hot Roads mentioned and under hood temperatures can bring on vapor lock!

Have you change the fuel filter/accumulator lately? It's down there by that hot road and "If" it is restricting the volume amount to the fuel rail then preheated gas will boil more easily. A reduced volume is also a reduced pressure and bubbles will form more easily.

If you have changed that out.....?

You could try putting some sticky insulation wrap about 1/4 inch thick onto the fuel rail at its connection point and backwards to the very end of the fuel rail near the firewall area.
It works out to about a good six inches of length to cover the metal tube.
If one had too, some bits regular fiber glass insulation wrapped with aluminum foil can do the job until a more waterproof or automotive type material could be utilized.

The rubber line changes to metal right there.
That rubber line is the highest point of the entire system.
A fact of physics is....All bubbles will rise to the top or highest point of any liquid system because vapor has Less density, therefore, less gravitation pull.

This happens while in a flowing motion too, trending higher inside the lines. As they accumulate they grow larger and are more susceptible to becoming superheated displacing more fuel volume.
The logical reasoning for the insulation in that location!

I have had it on my '86 so long I forgot that it was there. I used to live in Southern California when I got the car! The only car I have had to put it on too. None of the other cars I have picked up since, had to endure that hostile environment! (:/). Except my '78 K-jet.

Running on two cylinders is bad enough that you would barely be able to drive it. On one cylinder I'll bet is impossible. You may have been alternating between to bad ones.
I want to say the rear two ones as they are the first to get fed the least along the rail! They would be the path of least resistance for fluid to flow to fill a void created.


Its worth a try!
A lot cheaper than all new pumps and far easier to install.

Phil

This may sound like "diagnosis by parts replacement", but I'd suggest getting a known good ECU and swapping it in... See what happens.

If no change then at least you have a working back up ECU, and having extra working parts is always good.