Strange idle issue

The issues would come and go, even after playing with the carb. I recently checked the distributor vacuum advance diaphragm, no vacuum tool, it seemed fine. Guess it must have have a small leak because the issue would come and go. Now it was all the time. Checked timing and it was low. ( I run full manifold vacuum) Rechecked diaphragm and sure enough, has holds no vacuum at all now. So I capped the carb vacuum port and and retuned everything and all is well now.