Where is my shift throttle housing located? on 1992 Mercedes-Benz 400SE

Approximately every year and 1/2 depending on how much you drive the car in a year's time,it seems to lose power or feel like it is out of gear. Then, when you accelerate heavily to keep the car moving, the RPM's go way up and it is making the engine race really high.

Asked by for the 1992 Mercedes-Benz 400SE