maxim
what is you vehicle ??
because if it is a series 1 rb25det they have weak coils in them and sometime when they are trying to fire iridium spark plugs they dont work to well because of the lower grade coil.
if it is a series2 rb25det then you should have no problems running iridium plugs..
get some carby cleaner and give the coils a good clean with the cleaner , outside and up inside where the plug contacts the spring of the coil..
if you have something different then ignore the different series of coils info..