[A/SP911]

I have a strange problem in that just one of my secondary plugs in my 964 engine is not showing any signs of spark as it is untarnished after running hard around the racetrack (all other 11 plugs show the right amount of "soot")

I have tried three different tested plugs, grounded this cylinder #2 lead a couple of times and it has a nice strong spark, belt is good on the distributor, and I am running a good quality Clewett wires that are making a nice audible click onto the plug.

However this cylinder leak down is at 83% cold while all the others are between 89-94% if that makes a difference?

Any ideas?

Thanks
S.Chapman