On the valve cover. I dont know how the engine bay is setup. But underneath the plastic on top of the engine there should be a rubber line running from the valve cover to the intake. It replaces the line on the valve cover. That's where it goes on the evo 7/8/9 and lancer 7th gen. On the valve cover to replace that line. It prevent oil from getting into the intake and giving it a "cleaner" sense of air. I would assume that you have the same thing on your engine at the top after you remove the plastic thing.