1967 Dart 273 2bbl odd fuel delivery issue at idle

Isn't it odd.

I have to assume that there is pressure in the filter preventing additional fuel from coming in and once the float lowers enough I suspect the gas vapor pressure inside the filter is relieved and fuel flows. I pressure tested the pump and got 8.5 lbs and it held after the engine shut off.
The float needle is sealing as there was pressure in the lines when I separated the filer from the lines.
The engine was cold at the time I tested the pressure so it might be a heat related issue. I'll recheck the pump pressure when it is hot and with a "T" in the line after the filter to see what the running pressure is.