I am replacing the O2 sensors while I have my engine out for a DIY top-end. It is clear that the engine had been out before, and the person doing the work didn't pay great attention to detail.

When the engine came out, there were no cable holders for any of the 4 O2 sensors. I could not find cable holders for the O2 sensors anywhere in the catalog. Are there supposed to be any? If so, any help in finding the part numbers and proper locations is much appreciated.

 

I only replaced one of the sensors nearest the right rear of the exhaust system. I seem to recall it had a hold-down with a screw tieing down the pigtail up behind the bumper.
If you go fishing on this site you will probably find a picture(s) of what you want to know under replacing oxygen sensors. Or check p-car.com.

 

Hold downs for the O2 sensor wires, I don't believe are Porsche specific parts. Simply use a properly sized cable hold down clamp that can be held in place by any of the studs on the engine or related hardware. Buy clamps that are sleeved in plastic or rubber to prevent chaffing of the cables.