The system I'm speaking of is a hybrid where the throttle body has a electric motor and clutch plus an actual mechanical linkage. The electric motor can override the linkage.

Have a look here for a 94 E230 http://www.w124performance.com/docs/mb/M104/M104_ETA_rewiring.pdf

I know at least the M104 ASR cars had this, I have a 1991 300SL with such a system and a motor from a 96 E320 that still has this type of arrangement

97 was the first year for true drive by wire ( no linkage between the pedal and throttle blade ) at least on the SL320 , C280 , E320 .

Have a look here for a 94 E230 http://www.w124performance.com/docs/mb/M104/M104_ETA_rewiring.pdf