Sounds like they didn't have the choke working properly, so the used the breather stud to hold it open all the time. The spring is heat activated, and the adjustment controls the temperature when the choke closes. The tube is supposed to be connected to a sheet metal housing on the exhaust manifold, but if you cut the end of the tube square and run it to where it butts into the manifold it will work. When the manifold is cold, the choke should be closed, as it warms the choke will open.
