between circuit miss?

Ironmike said
so now in the car I have this annoying miss right around 1800 to 2000, only at cruising speed(very light throttle). I think its having trouble between the idle and main circuit. Give it a wee bit more throttle and its gone.

"Idle" Circuit

Ironmike said
Engine makes about 10 inches vac, at 1200 RPM idle,

WAG because I know nothing about the engine but this suggests the throttle is set too far open to begin with.
Use the guidelines for initial timing in the "how to" section.

Ironmike said
Tried upping the idle air bleeds from 74 to 78, with no perceptible change.

Its the combination of Idle feed restriction and idle air bleeds that determines how quickly the fueling drops off. BUT, the transfer slot is also a variable restriction and air bleed. That's why getting the initial throttle position ballpark is important.
You can certainly experiment with the current setup you have just to see the effect. But if you don't see any, now you know why; the other variables are overwhelming the effects of IAB changes. Try dropping the Primary IABs to .070 or so. It should effect both base idle and off idle. You can also just stick your finger on an IAB and see if it has effect on idle. If not, then changing them won't do any good for sure.

This will give you a generalized idea of how air bleeds work. However with the idle circuit its a little different than shown. For idle we want it to taper off and also fuel flow at even 600 or 800 rpm is already somewhere close to the middle of the graph. Finally of course there are no idle "emulsion holes" in the Holley Idle Circuits.. Air Bleed Characteristics