Intermittent crankcase pressure issues

Are the baffles in place in the valve covers for the breather and pcv ports? Where do you have the PCV plumbed in to? What weight oil, this may effect how fast it returns to the oil pan especially with high volume pump. If you are running a non stock breather (no hose to air filter housing) it’s very possible to have more blow by at higher rpm. With the throttle blades open further the vacuum in the intake moves more towards atmospheric pressure. This causes the PCV to draw less and that is the point the factory style breather with hose to air filter takes over.