When replacing the wiring loom can you replace with a loom from another car as long as the loom manufacturer codes match up with yours? Will this cause any issues? I see a swap with matched loom codes as a like for like swap, is this correct?

Probably, but which loom are you replacing and why?

It's the engine wiring loom, mine has oil in from cam magnet leak. Unplugged lots of connections and sure enough they are oily inside. Ecu not been bothered by it although there is traces in connector. I've seen a matching loom same full 271 code so was wondering can I just replace with this?

Having replaced more than one connector recently due to breakage from age and heat, and knowing how they are made, I would not replace my engine wiring harness just because I had oil in some connectors. Go buy a can or two of the fast evaporating style of electrical contact cleaner and just spray them off good. That stuff just eats oil. Walmart sells it for about half what the auto parts stores do.

On the M271, there is a defect where oil leaks from the camshaft sensors into the wiring and wicks into the ECU. MBZ's solution is to replace the seals on the sensors, wiring harness and also add some pigtails to create a "drip loop" to keep future oil leaks out of the ECU.

This the issue- I have replaced the cam magnets and also fitted the pigtails, however the oil is within the loom already, I can continually clean the ecu connector however some connectors are more labour intensive to thoroughly clean through with cleaner spray. I have seen a loom with the same code as mine so thought if I fit this the oily loom is no more and the connectors won't require cleaning again.

Hmmm, guess I'd need to see how far that is to wick on that engine.

I guess I am confused as to why you don't just buy the proper loom and replace it. Have you found a used one you are trying to use?