Where should this connect?! EGR? Vac?

[Skorpyo]

I was installing a new water pump and decided to reinstall the air box. I maybe should have paid better attention but now that the air box is back in one line seems to be “sucking air”. When capped the idle returns to normal so I’m guessing I dorked something up. Can ya’ll tell me where this port should connect? Is it to the back of the airbox? 
 

Thank you!

[fiatslug87]

Yes to the back of the air box.

[Skorpyo]

Thank you, that was my suspicion just couldn’t make heads or tails of it from the diagrams I found!