I changed all six plugs and definately made sure the wires were clipped. No change. None of the plugs look out of the ordinary. Not excessive rich or lean. He said when it happened, the AFR was 12.6:1.
I've given them a call to try and lay my hands on the file (they don't normally give them out but because of who my g/f is they would "see what we can do") but he said to call back on Monday.
