mystery vacuum hose

Hello,
I'm just wondering if this is a vent hose or something. It was taped to two other vacuum hoses along the firewall. Any ideas?

http://files.automotiveforums.com/gallery/watermark.php?file=/503/240769mysteryhose.JPG

Is there a little plug on the end that's kickin' around in the engine compatment? On my totally lame CPI rig up, there is a vent tube by the tranny dip tube for the trany. On the passenger side firewall (well, within the vicinity) is the transfer case breather, and in front of the ABS unit's the vent tube for the front diffy. All are terminated in little round black plastic caps.

That should connect to a T connector that also runs to the vacuum ball.