Hey Glenn, did you check to make sure the secondary plates are not binding? Open the primaries all the way and then check to make sure the secondaries open freely and are not stuck. The vacumn diaphragm has a cork gasket between it and the carb, it's in the port between the two close together mounting screws that hold the diaphragm chamber to the carb. If you have an electric choke you need to remove it to get the vacumn chamber off.