Air:Fuel Help. Cannot Get it Rich

dilweed said

I'm guessing 525ish HP, so I too think I'm adequate on the lines and parts. The car was running great with a cheaper less flowing pump, and 6AN supply line dead-headed at the regulator.
Prior to running the Mallory return regulator, I even used a (new out of the box) Holley dead-head regulator and ran this new pump with 8AN from cell to regulator since I was in a hurry to make a track event. Same issue.

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Maybe something stuck in the pickup tube? If you get a pressure gauge in place and run it once-twice hard while observing for any pressure drops, you will know right away if something in the delivery system before that point is amiss. You never know how a couple of things can add up and confuse matters: maybe the old pump was giving out and the new one is not up to snuff.... You just gotta get a direct reading on the pressure to the carb under load IMHO. At least the intake seem sounds after your testing there; those were good suggestions to find intake leaks.