For what its worth, I harrassed this board with pressure amplifier questions etc, re: a vacuum leak and transmission shifting harshness. Well I finally fixed the problem. It was a $60 part from MB called a pressure converter, its a blue plastic device on the drivers side fender. A few people I spoke with told me that they don't go, however I'm here to tell anyone interested that they do. I hope this is helpful for anyone with a 85 123. Thanks again to everyone for your help...

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85 300TDT 456,000 orig. miles