Besides the fact that I agree that the Holley pump is less than desirable, not to mention its louder than my fricken engine, here are two other things I experienced withe fuel delivery. I would get a bubbling noise in my tank when the pump started running slower and my Fuel Pressure gauge would go from 7 to like 1 after about 1 hour of driving. I tried everything to fix the problem, then found out what it was.....
VAPOR LOCK in the front carb bowl (could here it boiling). Now this was in Texas and it gets hot there. I actually tracked the temp outside that starts it....at 85 deg F it will start doing this (with hood on ofcourse). I stalled at the track several times with hood on because of it. Thats why I run with the hood off in the summer......because IT WORKS! If you dont have a fuel reg, plumb one in to track. Try running with your hood off and see if it cures the problem.
Terry