Also, if indeed the coil connector(s) is/are bad, wouldn't the CEL come on and throw a misfire code? Not disagreeing with you (man I hope it's that simple) - just thinking out loud here...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280