An extreme misunderstanding by a previous owner?!
I can't quite see, but Douglas commonly used a warm air muff on their AMAC carburettors, in which case you might find that the connection at the carb end doesn't go into the intake manifold, but instead into a gallery around the intake tract. If so, the other end doesn't connect to a fuel tap (!!) but instead to a collector of hot air off the exhaust pipe.
Leon