[cmonref]

The old AAV fitting goes to the starting injector location which then introduces air below the throttle plate. As you note, the CIS hooked the oil tank breather to the boot between the metering plate and the throttle. Other cars hook the breather just downstream of the filter.

I always figured the hole in the CIS restrictor was intended to let air flow but to keep oil that has condensed on the walls of the hose from entering the intake boot.