I am with ctaylor, I would go for a very thorough cleaning of the idle control valve (ICV). And checking of the hoses attached to it. I had the same problem (with hunting idle) and the cleaning of the ICV fixed it. Remove it and use carburator cleaner.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
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