[55blacktie]

The "mushroom caps" on the manifold are part of the heat riser automatic choke system. There is a metal cross-tube inside the manifold that is also part of the choke system. Often those tubes have disintegrated, but they can be replaced. If you look on the passenger-side exhaust manifold, you should find what looks like a spacer, where the down pipe joins the manifold. That spacer is the exhaust choke valve. It could be that your problem lies somewhere within the choke system. I would beg, borrow, or steal a proven carburetor/w electric choke, and see if that fixes your problem. Best to focus on one thing at a time.