Don, I think you need to complicate it even further . Keep the breathers on the valve covers but add a check valve so air can only flow into the motor, not out. Put the vacuum pump suction down low. Off boost you get airflow into the valve covers and down into the motor which will sweep all the volatile vapors along with it and out the vacuum pump. On boost the blowby starts to pressurize the block and the check valve closes so there is no more flow path for the blowby upward to fight against the oil trying to drain downwards. Yes, for the duration of the boost you aren't efficiently keeping water out of the oil, but all the rest of the time you are which should keep it clean.