John,
I'll be interested to hear what you find. You are taking a very methodical approach so you will very likely figure it out soon.

I have read recently on the Ritter/Easley list that some aftermarket motor mounts are pretty lame. Even the factory ones don't last as long on our vehicles due to the V-8 (though sounds like yours check out OK). Did you know that the corrugated plastic ducts under your front bumper (if it's like mine) are there to route air to the motor mounts to keep them from frying from the higher underhood temps of the 400/500E?

Do you get your engine to do some heavy breathing (aka Italian tune-up) regularly? I started doing this about every week and it helps at least a little. The first time I did it, the engine started missing at about 5000 RPM. I persisted, and that's a thing of the past. (Stu Ritter had said that that would happen-- you just need to not lose your nerve and keep pedal to metal ...)

__________________
Steve
'93 400E