The throttle actuator is 750GBP from Benz in the UK. I cured my ASR issues by three cable ties - cost 1USD!
Check your accelerator outer-sheath is OK.
Check your accelerator cable is adjusted correctly
Check Jim's web site for more info
http://pages.prodigy.net/jforgione/MB_asr.html
Lots of good links here so follow them and read.
SEARCH in this forum as there are a several excellent posts regarding technical ASR fixes.
Hope this helps
Lea