What does the adapter that is connected to the trottle housing connect to on 1999 Ford Expedition

On the engine it is connected to the PVC tube and to the front Intake what is the other tube facing the rear going to

by in El Paso, TX on July 18, 2013
1 answer 4 comments
ANSWER by on July 18, 2013
poss vac port of intake manifold
COMMENT by on July 18, 2013
Does this at all connect to the cooling system
COMMENT by on July 18, 2013
Look at digram under the hood.
COMMENT by on July 18, 2013
Does not have diagram this is why I needed Help
COMMENT by on July 18, 2013
I guess i have just been lucky enough to work on those that do.