I had a series of problems with my 93 600. I also reved it from the throttle cable, but I was lucky no ASR light came on. The reason people seem to suffer from this problem is because the wiring breaks down over time (the plastic shielding just breaks up and it shorts out). Lucky for me, my mechanic didn't want me to have to spend the thousands of dollars to buy two new actuators (if one goes the other soon follows) so he send it to a computer guy who actually rewired the thing (both sides and main loom) for a few hundred bucks. It's running better than ever now. I only had it done about 2000 miles ago but there is no sign of trouble yet (touch wood). Here is a link to what it looks like and the wring breaking up. http://www.mbnz.org/gallery/showlink.asp?CatID=12228&parentID
=26&subname=SL600_throttle_body_damage&parentname=R129_SL_Class

Hope that helps.