can a bad case breather cover cause a vacuum leak?

[kamaro]

I have an idle issue in my car for a while now ('76 with a '86 3.2 engine), I traced it down to a vacuum leak just because rpm is not changing if I remove the oil cap. I took a carb cleaner can and started spraying on all suspected places until I sprayed on the back of the throttle body when the engine rpm went down and stalled, I pin pointed it down to the case breather cover (which has a thermo-switch and a large rubber hose connected to the oil tank), does that indicates a vacuum leak related to the breather cover?, does the engine case it self connected to the intake vacuum?, I need to confirm that before I start removing parts to reach to that area.

[john walker's workshop]

SCs and 3.2 Carreras were sealed crankcase engines, so yes.