Originally Posted by ILUVMILS

The idle speed can be raised by about fifty RPM and the engine control module software can be updated to give the car a little more power. It's also possible that the high ambient temperature has placed a greater demand on the A/C. Remember, the A/C compressors on modern MB's provide variable output based on cooling requirements. With increased cooling demand the compressor is placing a much greater load on the engine, possibly causing the vibration.