[QUOTE=locum8;6315800]It's a 2009 focus st running at stage 3 level. The problem is that spark plug number 5 keeps burning. I've tried rs plugs and a colder denso iridium but to no avail. The plugs last about a month and then it starts to miss fire again and I have to stick new plugs in.

I took it to hypertech for a dyno run and it ran fine on the dyno, the guy was very helpful btw I would definitely recommend, but like you say they are more a Japanese specilast and I was looking for someone who deals more with fords.

I've heard mixed reviews about ava, some swear by them and others wouldn't go near them. Things like they are very hard on the car on the dyno etc. but I've not got any first hand experience with them.

I was thinking of sitech but now I'm not so sure.