One thing to note is that Holley terminology can be misleading. The "idle" circuit is more of a low speed circuit that boost fueling before the booster gets fuel moving. The idle mixture screw merely releases air and fuel emulsion from that circuit to below the throttle plates.
A lot of tip in stumbles are really just a lean idle circuit. People bandage over it with big accelerator pump cams and squirters, but the real fix is in redrilling the idle jets, which are a fixed part of the metering block in Holleys. Better aftermarket carbs have replaceable jets for the idle feed restrictions, but if you don't want to buy a set of aftermarket metering blocks, ONCE YOU HAVE THE IGNITION WORKING OKAY you can get a pin vise and small drill set and carefully open those up.
What you will probably find is that tip-in and low speed drivability get much improved, and the idle mixture screws get more responsive instead of needing to be 3 turns out...
