"Factory" vacuum leak???

I bet the piston in the carb has been removed and allowing too much air into the choke housing causing the arratic idle.
Now, having said that, is the OP absolutely SURE there are no other vacuum leaks on the engine?
Is the PCV valve the correct one for the engine?
Are the correct heat range plugs installed? If too cold a plug is used the engine won't idle correctly.

In order to eliminate all this hokus-pocus (if it was my car it would have been done already) you can always remove all this electric/vacuum automatic choke control BS and install a manual choke cable. This way you can plug all these mystery holes and be done with it.

George