If the vacuum advance will not hold a vacuum, then I would replace it before looking for anything else.
You may have additional issues; but fix the one you know is bad, and see what happens.
Jon.
X2
My engine ran like garbage until I figured out the vac advance was toast. I doubt that is THE issue here. But might as well just knock it off the list.
If you can’t find a replacement right away, at least plug the port.
