The reason the ovp can cause this is that it supplies the CIS control module with power.With the ECU not powered up,the engine will idle too low and rough because the idle air valve is now dead.It is blamed for a lot rightly so.That is normally the first thing I check on any car with an OVP and a driveability complaint.
What many people dont realize is that most CIS engines will run almost as good (exept at idle)with no control unit at all.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."