Missing O2 sensor causes of rough idle and running rich?

[dgwestfall]

On my 1993 300 SE Mercedes, it appears that someone has removed the O2 sensor and replaced that section of exhaust with a straight pipe. Would this cause my car to run rich and idle rough? I replaced the fuel pressure regulator and this helped a good bit, and a car drives really well now after replacing that and fixing the cam advanced magnet system I know on some cars it doesn’t really affect them too bad if the O2 sensor is cut out of the system, but being a Mercedes, I can’t imagine this isn’t causing my problem. I’ve already replaced the plugs of wires, cap rotor, and coil and I don’t have any vacuum leaks. I have a new O2 sensor on the way, and I plan to have my exhaust shop install a new bung for the O2 sensor.