In moderns M110, the 1981-1985, i guess they did came with an Oxygen Sensor. can someone provide me with a picture of the actual placing of the sensor, does it go on the manifold or down at the exhaust pipe.

On my 1980 280SE (W116) with the M110, it was on the exhaust down-pipe about 6 inches from the manifold. The sensor is oriented so that it faces the rear of the car - that way if any moisture is running down the pipe it won't end up in the sensor.

If you don't already have a bung, you can weld in a "spark plug non-foul adapter". Cut the unthreaded end off, drill a hole in the pipe, and weld it in. The o2 sensor screws into the threaded end.

Any exhaust shop should be able to install the bung. I have only seen 18mm threads on the O2 sensors. Sparkplug non-foulers also come in 14MM. So be sure that the bung that you weld in fits the O2 sensor.

__________________
"If it's in the newspaper it must be true." Dudley Do-Right