Q: No power when accelerating

A faulty throttle position sensor can most certainly duplicate all of the symptoms that your Mercedes is experiencing, however a faulty fuel pump or even a defective mass airflow sensor can be the cause to these issues too. I have many times installed a brand new mass airflow sensor on a vehicle, only to have had them fail right out of the box in pieces. I recommend enlisting the assistance of a certified mechanic to come by and inspect your Mercedes with you before making any more repairs. They will have all of the tools and the experience necessary to identify exactly why your Mercedes is having a lack of power. They will also be able to perform the repairs necessary to restore power to your Mercedes so you can drive worry free.