Timm, on my '82 380SL the engine fan thermocoupler failed about a month ago, and caused the car to run very hot and the aux electric fan to come on when it really shouldn't have needed to. You might want to check yours out, or just replace it. After replacing mine the car runs right at the bottom of the range unless it is REALLY hot and the A/C is working hard.
As regards the WUR, holding a vacuum doesn't remove the WUR from the suspect list, as what usually goes wrong is that a spring inside the WUR loses it's tension and allows the control pressure to go off spec, usually causing the engine to run rich. The only real valid test on the WUR is to check the control pressure. A quick and dirty test is to very lightly push down on the air plate and see if the engine runs smoother. If it does, it is a sure sign that the control pressure is off.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C