I just thought of something. There is a diaphragm that mounts on the carb cover, is triangular shaped, has a cap that has a raised cylindrical center, mounts with two of the cover bolts and a third, and may be part of the system we've been talking about. I'm not home to look at it yet, but I know that Haynes had a name for it on the carb diagram but no description of its function - could this be it? I wish I could remember the name or what passages connect with it. Any ideas?