If I were to hazzard a guess, it is a vacuum hose for a power brake booster. Runs from manifold to the hole in the "can" to place a vacuum on the diaphram. Not sure what the small diameter port is for unless a vacuum guage could be hooked to it for a test.
As soon as you find it on the teener, let me know, I've been looking for mine
Do I win the money?