what does this valve connect to?

Earlier today i was replacing my spark-plugs and i had a hard time taking off the air
intake manifold. after i removed, all the valves, plugs etc, i replaced the spark plugs
and i put everything back together except this one valve, i looked for any missing
connections and i couldn't find anything, i assumed that it wasn't suppose to connect
to anything and i put everything back together and then my car had a rough time
starting up and my fan was blowing really loud. On top of that my engine light came
on, and my temperature gauge wouldn't move even after it was warmed upp. its the
white piece connected to the transmission dipstick, help me ouit!!