Holley stumble trouble

I was also wondering how the OP made out :)
I have almost exactly the problem described in the initial post (lean stumble at very small throttle tip-in and low RPM), except I'm running a QF 950 and I have a wideband AFR meter. My cam is a .652" gross lift mushroom ([email protected]) and idles at 1100-1200, 8" vacuum, 13.5 AFR, in a 451 with RPM dual-plane. 27 deg idle timing, 35@4000, vac advance.
At the very beginning of tip-in, the AFR will jump to 17-18:1 and of course there is a huge sag. Opening the throttle just slightly moves past that point, the AFR drops to around 14. No slack in accelerator pump linkage.
After much tuning last fall/winter (see the multi-page thread on racingfuelsystems Holley forum "Dialing in my 950"), I have concluded that I'm asking the impossible to have economical cruise AFR, correct AFR at WOT, and perfect driveability below 1800 rpm with this much cam! :realcrazy: I may have to either live with it, or cover it up with squirters/pump cams...
The unique problem with really big cams is that the idle vacuum is much less than cruise vacuum. 8" idle, 15" at 60 mph cruise in my case. I think there's no way to achieve perfect tuning with the vacuum going the "wrong way". Anyway I'm living with it ;)