Made some progress today. On a whim, I clamped off the return fuel line and took it for a long drive. Ran great, no surging or starvation at all.
of course, this leads to a couple questions.
First, The car no longer has air-conditioning… What was the purpose of the return fuel line on air-conditioning cars in the first place?
Second question… What could be causing excessive fuel to return? Perhaps float level?
third question, what prevents me from just disconnecting the return line and moving onto the next challenge? (I typically like to find root causes, but if this works, I’ve got plenty of other things I can be doing.)
as usual, thank you for all the help.