my latest method for cleaning/clearing the vac lines going through the key switch. disconnect the two vac lines - one going to the shutoff valve (brown) and the other from the vac source (green).
take volleyball hand pump with needle-
place needle into green line - pump like hell til oil stops coming out of brown line. you're done! ...at least til it clogs up again which for me varies 2-4 weeks.
cost=free

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1984 300D Turbo - 231k....totalled 11/30/07 RIP