Idle Transfer Slot on secondaries?

PCV. Once you have the idle timing correct, adjust idle mixture as best you can.
With the engine idling, in gear, remove the PCV [ it will probably be in the valve cover ]. If it is rattling, it is not working; there is not enough vacuum to overcome the internal spring.
If the pintle is not moving, gently push on it with a small screwdriver. If the pintle moves, it is not fully seated, which is also bad, because the pintle has a tapered seat, so the air being drawn past it idle will vary & make it hard to get a consistent idle.

Bottom line: PCV pintle needs to be pulled in with no movement at idle.

Fix for low vac there is an expensive Wagner adj PCV....or what I have been doing for many years: get a 3/8" bolt, & cut off about 5/16-3/8" length; drill a 1/8" hole through it. Push this into the PCV hose. Job done.