Help please. Intermittent fail.

[Galwaylotus]

The run went reasonably well on Saturday. It was slower than I'd like as there were a lot of older cars running in front of me on narrow roads. As the run progressed I was getting a bit of a misfire while running at 1500-2000 rpm. There is also quite a bit of crackling and popping on the overrun. The misfire got worse as we got slower and the return run back wasn't any better. In fact it seemed a bit worse. Today I pulled the plugs (NGK BP6ES and running Powerspark electronic ignition) and photographed them. I'm hoping it just needs a good fast run on the motorway to clean things up but haven't had the chance yet. I don't know why number 3 cylinder seems to be cleaner than the others.

[gjz30075]

Wow, a lot cleaner than mine (same plug). And I don't have the symptoms you're experiencing now. I think
you still have a ignition issue.