Searching for a source of a vacuum leak I have come across the 2 controllers under the air-filter box (part#001 540 79 97). Even though they are located side/by/side, they react in a different way when tested with my MityVac. The bottom nipple and the one directly above it hold vacuum in one of them and in the other the bottom one does but not the one directly above it. In addition, there are two other nipples on the top "dish" that act the same on both. Does anyone know how to test them? Also, the newer version has only one nipple on the bottom and 2 on the top so it is not the same thing(must be some inline change that happened over last 20 years...). Appreciate any insights.