Holley/Demon Carb stumble

Is that Mallory regulator designed to go from 87psi to 9psi in one stage?

Have you ever put a gauge on the inlet side of the regulator to see what the operating pressure is on that side of the system?
As the demand is increased, does the inlet pressure drop as well?
If it does, does that impact the effectiveness of the regulator to maintain the outlet pressure?
I think this is where the idea of the dual stage regulator has merit.

My primary concern isn’t that the pump can’t supply enough fuel.
It can....... it was about 50 seconds for a gallon@6psi.

But....... it won’t at the pressure setting you’re using(9psi).
If the pump will only maintain 6psi at WOT, but the floats were set with the pressure at 9psi....... then the floats drop as the car moves down the track as the pressure is falling.

You’d be surprised how much a float has to drop to uncover enough area in the N/S to keep up with the high demand at full power/wot.
When you lower the pressure....... the float has to drop even further to make the area at the N/S even bigger.

The lower the float, the lower the fuel level, the leaner the mixture.

You tell me...... what’s making your motor lay down, 1/2 way through high gear....... after it’s already pulled cleanly through 2 gears.