You mean the one all the way on the passenger side on the firewall side of the valve cover that's part of the PCV system? That will depend on the engine. On my T-5 car, there's the Y shaped plastic fitting coming out of the valve cover, and the branched part of the Y goes to the hard line and the straight part of the Y goes to the PCV check valve which I think goes to the throttle body (but that's from memory, not looking at the car).