correct because the one that goes to the intake manifold has the pcv valve in it so it operates under vacuum, but when you boost the engine the manifold has pressure and the pcv valve closes so pressure doesn't enter the valve cover. The other side has the elbow that goes to the intake, because their is no pressure going to the valve cover, just a vacuum under boost so their is no need for a pcv valve one the intake side, thus thats where the catch can should go.