this is from holleys question section, i also think the fuel pressure is a tad high @ 7 lbs, 6 lbs is a more realistic number for the set up.
i can remove my fuel line and @ 6 lbs fill a 5 gallon jug in about a minute with about the same pump you have.

QUESTION I have a vacuum secondary carburetor that bogs when the secondaries come in. What will cause this?
ANSWER Bogging and hesitation are caused by the secondaries coming in too quickly. You can install a heavier secondary spring and this will prevent the secondary from coming in too soon. If the engine is sluggish in response at full throttle then the secondaries may not be opening soon enough. You will then need to go to a lighter spring. The spring kit is part number 20-13 which will have 7 different springs to fine tune with.