Is my Vacuum too low?

The transfer slots are the main fuel delivery system for the low-speed circuit. The mixture screws are the idle trimmers. If they get out of sync, then you have low speed problems.
The principal ways they get out of sync are;
1) too much idle timing,which causes the idle-speed to be too high and so you close the throttle valves, and boom there goes your sync. And
2) another way is not enough idle-timing. This causes a slow idle, and in compensation you speed it up.. and boom, there goes your sync. And
3) of course vacuum leaks wreak havoc with the sync too, as do
4) plugged low-speed orifices like air-bleeds and emulsion holes, and
5) a faulty WET fuel level in the bowl..
So the first place to start, assuming your carb is in fact clean internally, is always the WET fuel level, and the T-slot sync.
The best way to set the T-slot sync is to pull the carb off, make sure it is at curb idle and stays there. Then flip it upside down and eyeball the slots under the valves. They should be about square to a little taller than wide. Set them there and adjust the mixture screws to 2 turns from lightly seated. Then verify the float level and then put it all back together. After this don't touch the carb.
Set the idle speed with ignition advance/retard. Once the speed is close, you can twiddle the mixture screws for best idle quality.
If you find the best idle quality is with some adjustment other than 1.5 to 2.5 turns out, then the transfer slot is not right. If you had to richen the mixture screws, then put them back at 2turns out, and increase the transfer slot exposure under the valves just a tiny bit . If you had to screw the mixture screws in , then the Transfers are supplying too much, so drop the valves down, just a smidge.
After you finish that, you might have to change the idle speed BY ADJUSTING THE TIMING.
If nothing seems to work; go look for a vacuum leak, or if the quality of idle is bad, then firstly check the WET fuel level in the bowl, and if that is good, then the carb has to come apart again and the low-speed circuit cleaned out.
If you find the idle timing ends up TDC to 5*Advanced, don't be surprised;that is the factory setting.
The above assumes the engine is mechanically sound,and the valve timing, is right.