Yes after replacing the Imco regulator and new diaphragm/spring in the carb, it did the same thing.
With hose from air cleaner to valve cover disconnected, I plugged the end that attaches to air cleaner with my finger and it was able to build vacuum on my finger and on the small vacuum hose that attaches to the top of the carb. Can now accelerate just fine until I remove my finger? Seems like it needs a pcv valve in the line to build vacuum but there isn't one there??