Originally Posted by Stu @ M Developments

James (Or I?) will have meant that you have to be extremely carefull when gapping the Denso iridiums as the 0.4mm centre electrode is quite brittle and can be bent and even snapped. We gapn them all the time but for your setup out of the box at 0.7mm should be fine and no less. certainly NEVER less than 0.6mm on any cossie. Any lower than that needed and you have other problems.

Also, do NOT overtighten them. This is what causes the centre insulator to crack. Overtightening them stretches the casing (as does any bolt) and this can be an issue. Just factory specified tightness and no copper grease or other stuff some folk like to fit.

For the record, I would use IK27s on yours.