I removed the plugs and found that number 2 was burned ( electrode was a sort of pitted grey colour, looks a lot like a piece of metal after it has just been sandblasted ) and number 5 plug the electrode was completely burned away.

The plugs where only fitted a few months previous so I was a bit worried.

So I put some new plugs in it and took it to the dyno and got it check out and the operator couldn't fault it.

The only thing he though was causing it was that as the car was running higher than standard boost the standard ford plugs where over heating and to fit a colder plug so I've been running denso iridium plugs for a few weeks now and it seems to be ok.

I will keep an eye on it but so far so good!