Just got off phone with service rep... apparently they have traced as far as the (signal ?) voltage to/from the throttle actuator... apparently it is somtimes there, sometimes not. They want to make sure that everything else is right before doing the substitution.
I again mentioned the issue with the wire harness and that the MB forums were fairly unanimous on the harness being a potential cause of the problem.
However, I did indicate that I was not trying to second guess, nor tell him what to fix; only that I was trying to offer any potential information that might help solve the issue.
Till next update; thanx
A mercedes is an inanimate object and therefore must respond to logic and reason.