I think you're getting the Throttle body and the Mass Airflow Sensor (MAF) confused.

The throttle body is a big chunk of metal with a huge hole in it with a butterfly valve.

The MAF is a plastic sensor a couple of inches long with a few (3 If I remember correctly) wires on it, that connects to the plastic elbow that connects to the throttle body.

It is possible that if you pulled your MAF you got it dirty or broken.... spray cleaners are available at parts stores to try to clean them. Unfortunately Mercedes sourced MAF's are known to go bad and need replacement.