Read this thread about code P0446 where I supplied information on the location and replacement of the Evap Shut Valve.
Code P0221 is a new one to me, but it does not only relate to the Throttle Pos. Sensor, but many other parts including the brake switch, ESP and so on.
After you replace the Shut Valve, clear all codes and see if Code 221 returns, and post back with findings.
http://www.benzworld.org/forums/w163...ighlight=P0446