With the early cars, the OVP has a metal ear that slides into the bracket which holds the ECU, ABS modules. So you just pull it out. The later model cars from 90-up I think had a 7 or 8mm set screw holding one of the ears in place.

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...