Found the problem, thanks for the advice. It was poor adjustment of the throttle valve actuator. One turn of the connecting rod was all it took. I think that the problem was very apparent on a hot engine as the heat from the manifold caused the rod to lengthen by enough to exacerbate the idle problem. Did not believe how sensitive this is, but that's what you get with MB...remarkable tolerances that need to be just right.

Really appreciate your advice,

g

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64 230sl, my daily driver
94 E500, sold
98 E320, family and dog hauler
04 C240, safe machine for teen drivers, but a poc
08 audi a4, yes we have gone to the dark side