that goes in the vacuum loop connecting the AC idle up solenoid to the throttle body
i think it T's with one of the hoses before the throttle plate that carries a one way boost blocking valve
it goes to the throttle body. the other end is pictured and is the carbon canister. its to do with fuel vapour emissions, i wouldnt worry about it. as long as the throttle body end is blocked off so no extra air is drawn it things will be fine