You have the older mechanical (diaphragm) type. It is operated by engine vacuum. It should be closed by default because the diaphragm is being pushed down by a spring thus pushing a pintle down into a pintle seat closing the passage. It is opened by engine vacuum when the vacuum overcomes the force of the spring. When opened the passage will also be opened allowing some of the exhaust gases to be recirculated back into the intake manifold and mixed with air to be combusted for a second time. You should be able to open the pintle and thus being able to both blow and suck air through the passage when you apply enough vacuum to the port on the diaphragm house.