Never use regular octane fuel in any MB after 1987!
Yes the system uses throttle by wire.
Have someone in service dept ride with you in their parking lot, if you can get the problem to happen all of the time.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator