Could be many possibilities:
1. The OVP itself is not likely to be bad BUT its contacts could have been widened. Remove and check, narrow the contacts.
2. Coolant temperature sensor (fuel injection temperature sensor) either is bad or its signals are not reaching the computer due to a broken wire somewhere. Check the connector on the sensor. A disconnection could put the car in a limp mode.
3. Check the EHA, this is normally providing enrichment during acceleration.
4. The air meter sensor, on my 87 260E there is a pot, I am not sure what you have on your car, could be the MAS, this can cause hesitation in the engine because the air intake is not correctly known to the computer
5. Check crank shaft position sensor, this can cause intermittent shutdowns. (less likely in your case)
6. Speed signal may not be availabe to the computer
7. Check vaccum, need to have about 20 on the vaccum gauge at idle, otherwise could be the catalytic converter

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Saumil S. Patel