well, you've got two problems here 1) the mixture is wrong and 2) the crankcase ventilation system is malfunctioning. To my thinking the environmentally conscious solution to crankcase gas formation (i.e. PCV) is secondary as it is nice but not absolutely necessary to the safe functioning of the car. Your car will run perfectly fine if vented to atmosphere. But, when the mixture is badly out (as sounds to be the case) the functioning of the car is compromised. In this case, it sounds like the mixture is out at least partially because of the 'spare' air getting in through the PCV. So, plug it off at the manifold and the crankcase is vented to atmosphere AND the crankcase system is no longer a source of air leaning out your mixture. You can get back to the environmental niceties of the PCV later. In the meantime, the combustion byproducts resulting from poor carburetion far outweigh the off-gasing of hot engine oil, etc. You still have to fix both problems independently but for now, the PCV problem is complicating the carburetion problem.