1993 300 E surging
 

1. just got a 1993 300 E 2.8 the car has a surge in the idle, code said replaced o2 sensor also the code called out MAF Sensor. However after replacing the O2 Sensor the wiring harness shorted out while pluging in the MFA sensor. I replaced engine wiring harness. Did not fix check the Actuator wiring bad replaced same codes. Took to dealer could not fix. Replace the computer the surge is gone however I have an fault code of 42. Help

I would start by building the code reader, learning how to use it, get the fault lists, etc. Do a search above for fault code reader, etc. It's not always the answer but it's always a clue and better than shooting in the dark.

Deterioration of engine wiring harness is a known problem with these cars.

Seems it might suggest not messing with things connected to the harness unless it's been replaced as it could risk a "short" as described.

DIY is filled with perils.

I'd build the code reader as suggested above.

I've never know an O2 sensor to cause a surging, though.

The usual culprits are, not in any particular order;

1. MAF sensor
2. Throttle Acuator (what you are calling the throttle body).
3. vacum leak

You mentioned that you cleand the throttle actuator, but cleaning is generally not effective. These actuators have defective wiring harnesses that also fail (and can't be fixed), as well as having potentiometers that wear out / fail over time.

Arthur Dalton has been particularly helpful with owners of these cars. Try doing a search for his posts and your problem, and I'm sure you'll find a ton of info to look at.