Going to work on Friday it decided to perform the "single cylinder" routine again.
I decided that with a service overdue I must make a start on it (it's a valve check service too - heaven knows when I'm going to find the time to get that done ...)
I whipped the plugs out and from the colour of them, concluded that it's running richer than a room full of merchant bankers on bonus day.
Getting the airbox apart I found the base of it with a good pool of oil (not so unusual) and the filter was as gunged and crudded up as a grungy cruddy thing ..... that'll probably explain why it's running so rich and probably explain why it didn't want to run that well.
Fortunately I have a K&N cleaning and re-oiling kit ... and am now waiting for the filter to dry completely following cleaning before I re-oil it.
The other thing that has been a royal PITA is that the tank has grown so much more that it would not clear the top yoke to raise it. The clips that you screw down must have overlapped the yoke by 7 or 8 mm (and last time I had the tank up it cleared the yoke completely).
On AF1 they have been suggesting that the growing tanks phenomenon is the result of ethanol added to the fuel (which also rots the fuel lines). Whether it's that or something else, my tank has grown considerably!.
I've spent quite a time modifying the various brackets that hold the tank in position. I've enlarged mounting holes as far as I dare and things now just clear the yoke .... I just hope it doesn't grow any more!
I'm now waiting for the paint to dry on the brackets so that I can put it all back together.
Clearly that's not going to happen tonight .... so I guess it'll have to be the car for work in the morning

Hopefully the plugs and air filter will have sorted out the running on one cylinder .... just the rest of the service to do now.