hello
not sure about the horn thing but the tube from the in take is a vacume line for the wiper motor
kevin
1930 model a tudor
1923 model t roadster p/u
The "horn" is the intake for a heater. It ducts air over the hot exhaust manifold into the car for heat. Usually there is a hole cut in the firewall behind the manifold heater to pass the heat and it doesn't look like your car has the hole cut. This was an aftermarket accessory for the Model A since they did not come from the factory with a heater. The line coming off the intake manifold supplies vacuum pressure to run the windshield wiper.