a pcv valve is best mounted at the front of the cover, not rear, with a large baffle, on a high accel. vehicle. the breather does not "vent excess vacuum" , it vents pressure when the pedal is to the floor and there is little to no vacuum
Good tip. My breather is just a simple push-in filter that fits in a a hole in the valve cover. It can let a given amount of pressure out or allow some air in to reduce vacuum, so yes, it can vent excess vacuum. Symantics.
