What Is This Part?

Some I am replacing a bunch of the small parts on my engine as I freshen it up with my build. I have replaced the temp sending unit and oil pressure sender, but I don't know what this part is on the manifold. I assume it has something to do with the vacuum, but I don't know what I am looking for to replace this. Would appreciate any insight. Thanks.

http://s1364.photobucket.com/user/W...7-48FB-A9E6-5EBB02C4DFD5_zpstxn4o8jm.jpg.html

http://s1364.photobucket.com/user/W...2-413B-B1CA-2F4ADFCFBEB1_zps9icfti98.jpg.html