No vacuum leaks. I sprayed carb cleaner around all points of potential entry, then repeated it with Ether. No leaks were found.
I just adjusted the idle mixture screws to 2 full turns out. The idle vacuum didn't change much but now it runs much better idling in gear. The prior setting was just shy of 1 turn out from the seats. Not sure why I had them set so far in. I think that I was trying to achieve the best vacuum # while idling in neutral. This time I aimed for a richer reading in gear. Before it would idle rougher and sometimes stall when accelerating. Now the rpm drop when going into gear is only 200-250 rpms. The A/F readings in gear went from the high 17s to under 13.0. It feels much more responsive off idle with the richer mixture. This carb has idle mixture screws in both metering blocks. I was surprised to see tha A/F readings changed by turning the screws in the rear metering blocks. I wouldn't have expected that. I thought the idle circuit was only related to the primary side.
Hopefully I'll have more time to tune over the weekend.