Fuel Fluke

I had a VERY similar problem. It was confounding yet I solved it.
I insulated my entire fuel line from the fuel cell all the way to the
carb with a D.E.I. (Design Engineering Inc.) product with a velcro
closure AND used a phenolic heat resistant carb gasket (3/8 inch.?)
Cool fuel, and a cool carb made my car run much much better. My
under hood temps were high (since corrected) and this heat made
my mechanical (oil filled) fuel pressure gauge make it appear that
I wasn't getting enough pressure. I insulated this too and it now
reads as it should. In short: keep your fuel as cool as you can between
the tank and the carb. I'm confident that this is the problem. Good luck!