Mercedes Benz repair: response to high idle on 85 380SL, oxygen sensor, 380sl

Question
I'm writing back about your questions concerning the mileage, etc... on my 380Sl. The odometer reads 139K, but doesn't work.( the speedo does )There is no corrosion under the hood and it is now idling at 2000 rpm all the time. Before it was off and on. There was an exhaust leak right after the drivers side catalytic converter, which is now repaired and it's been idling at 2000 ever since.  

Answer
Was the exhaust repaired with an electric welder, and was the battery disconnected during the welding?
If the battery was connected you have electrical damage.

If it was not connected, there is probably a bad oxygen sensor and/or restriction in the exhaust system the computer is trying to compensate for.