Vacuum Mystery ?

Are you sure there is not another breather opening, and how sure are you that this engine does not have more blowby than the factory ones beck then?

Factory performance engines, and I don't remember for sure about 340s, but 440 HP engines had a greatly reduced warranty and a VERY poor guarantee as to oil mileage. I don't even recall what that was, maybe 1 qt in 500 miles or something.