I found this on another thread. I don't know what the names of the parts are, but the piece in your pic looks like #18 and the vacuum line goes to #15.
Good luck!
EDIT:
It looks like #18 is the SAI Changeover Valve and the vacuum line in question is supposed to go to #15, the Intake Resonance Flap.
OOPS!! Please disregard the attachment below. It turns out it's from a 996 and I don't know how to remove the attachment.
So, in the diagram above, #15 looks to me more like an EGR valve or SAI valve?
Hopefully this helps, it's all I got.