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Chasing down an idle misfire on cylinder 3

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dennis10:
Hi all,

I'm trying to chase down an intermittent idle misfire that I'm getting on cylinder 3 on my Edition30.  It only happens on idle, hot or cold and not all the time, the engine otherwise runs faultlessly all through the rev range.  There are no fault codes or engine management lights, although I do suffer from a rough cold start issue too, which may or may not be related? - From web searches it seems there are quite a few cars with these types of misfires and I've gone down the route of eliminating all the usual.  Below is a list of what I've replaced/checked so far:

Spark plugs
Coil packs
N80 purge valve
Diverter valve
PCV valve
The car went to R-Tech and had a thermostat replacement, as well as carbon inlet clean and injector service.  They noted the misfire on cylinder 3 at the time and as the injector was slightly under performing compared to the others they replaced that 1 injector (I do not know if the idle misfire I'm still getting is still only on cylinder 3 since all this work, but I suspect it is - How could I confirm that?)
I've also replaced the original MAF sensor with a brand new Hitachi item.
One thing I noticed is that when I ran the car without the MAF connected, to test it, it ran faultlessly and had no idle misfire.  Plugged the old MAF back in and the intermittent misfire is back.  I thought this pointed towards a faulty MAF, but unfortunately it is happening with the new one too.

I've purchased a compression tester that is yet to arrive, but I'm not sure if the issue lies there as it is intermittent and disappears with the MAF unplugged.  The car doesn't use any oil or coolant, although I did notice a bit of oil on (I think spark plug no.3's threads when replacing the originals)

Please help me to work out what might be the issue that is ruining my (pedantic) enjoyment of what is otherwise a fantastic car

dennis10:
Forgot to add, when I replaced the spark plugs I poked my little borescope camera down the holes and took photos. Is there anything to be discerned from these? I think cylinder 3 does look a bit darker than the other 3 cylinders, but the spark plugs all had a healthy colour

Cylinder 1

Cylinder2

Cylinder 3

Cylinder 4

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