that has to be a direct port into the IM after the TB based on where it is.
If you don't have anything that needs that connection, plug it.

check out your IAVC and make sure your idle adjust screw isn't turned all the way in...

Since I don't really know the IM you're messing with.... what is the hole between the left two injectors? just below the fuel rail. it looks like where the PCV valve would go.