Have you relocated the IFRs to the lower positions? That usually helps a lot with the condition you describe.
Most all newer holley clones locate the Idle Feed Restrictions in the high location, above liquid fuel. In a lot of cases, you can tune the idle mixture to be correct, but when you get into the transfer slots, it goes lean or erratic. Moving the IFRs to the lower location under the fuel level really helps stabilize the idle circuit fueling.
I never really tuned a mechanical secondary carb until I bought my current '67. It had a QuickFuel 750-HR double pumper, and it ran like chit. I did the typical stuff but it was still fat and lazy.
I searched the internet high and low, Yellowbullet, The HAMB, Don Terrel's speedtalk, the Mopar boards, racingfuelsystems.com, here on PY, etc trying to figure out how to tune it. I bought a couple of the older Holley tuning books. Nobody covers the HSAB or the emulsions in deep detail. Its nuts how quiet everybody is on those critical parts of a holley carb. Tom V, Kenth and a few of the carb guys here were very helpful on explaining the advanced tuning approaches. Its in a thread somewhere here on PY.
Finally I found posts copied from the old Innovate Forum back in 2011 or so. There were some guys named Klaus and Tuner that explained two-phase flow in detail, and the cutaways on the below website helped me understand it.
Sorry for the long-winded posts, but I tend to brain-dump on carb threads now. Somebody in the future will come across this and it'll save them some time.
https://garage.grumpysperformance.co...59/#post-56233