Is that valve a plastic thing that screws onto the linkage side of the butterfly? Like you say it looks to only do anything at WOT. I did replace it, after putting the car all back together and it was a real pain to get at. I would have done it sooner but had trouble finding it anywhere, finally got the part number off Benzworld site. Sorry but lot's of good info over there.

Where is the PDF you are referring to as my CD doesn't show vacuum schematics having anything to do with my Euro car. Actually all my schematics show a throttle switch or TPS on the butterfly, something my car does not have.

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Chas

Had a 380SL, 450SL, 380SEL, 420SEL, 500SEL

Got a Euro 500SEC right now.