For some reason I can’t post in the original post, the system keeps kicking me out after I log in.
The road draft tube is an engine breather and comes from the passenger valve cover (sometimes the intake or other places on cars) on these cars I believe. It accesses and expels crankcase fumes. There is a air intake on the drivers side valve cover on my car where you fill the oil.
I may. be wrong here but the exhaust manifold provides heated air with convection through the tube to the choke at the carb which effects the spring and moves the choke. If it developed vacuum it would be pulling air not pushing air. The tube goes into a little cast in chamber on the exhaust manifold on my carburetor car. I have the plate off it, not using it as I have an Edelbrock carb with elect choke, it is open with no tube, and I do not have a vacuum leak.