Where does this pipe go?

[Radiohead]

Your papers please.
Uh, I only have a pipe, man.

 

[clickittyclank]

Just a small update on this. So far it looks like the folks who said it was an extra brake booster pipe were correct. Have it mostly hooked back up now and don't see any other place it could go. Somehow someway I've picked up an additional pipe over the last decade or two. Thank yall for chiming in and helping a dude out. Cam break-in coming soon. So ******* excited to get her back on the road!