Barry, if the plastic push-in valve/hose connection goes bad, it sometimes lets engine oil (via the long hose from the intake manifold) up through the valve and inside the booster. The oil attacks the large rubber vacuum diaphragm and over time can cause failure. In our Benditalia boosters, the diaphragm is not home-replaceable as a separate part. So its certainly worth pursuing this problem. Many power brake boosters use the same valve.
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