No used throttle actuator. New one will apparently arrive in the morning and be installed.
The service rep indicates that the original ecu will be reinstalled, and the car will be checked for codes. Then the onroad testing to ascertain that the actuator is the remedy.
The service rep is still puzzled over the fact that the error codes followed the original ecu when it was swapped from side to side in earlier diagnosis.
A mercedes is an inanimate object and therefore must respond to logic and reason.