I have a '73 Series III. I replaced the carburetor last week and noticed what I think is a missing hose or cap on an air intake tube on top of the manifoldjust in front of the carburetor. Can somebody please tell me what the function of this small air intake is? I'm pointing to it in this series of photos. When I cover that intake with my finger the engine runs slightly better. It feels like it should either be capped or should have a tube attached running to another place. Any help would be greatly appreciated.