Keep in mind the system Patrick has shown there helps with keeping
oil out the intake while at light throttle, normal PCV operation, when the other side of the engine would be supplying air to the crankcase.
This fresh air can be via a filtered cap on the valve cover, or a large hose to the air cleaner.
When on the loud pedal, the air flow is reversed, since blowby is much higher under load, and PCV can only flow a certain figure.
So if you have
oil around your breather cap, best look at the design of the filter/cap.
Gary