I put the Iridums in my '01 Cobra and they seemed to work pretty well... but, I replaced them at the same time I swapped the filter with a Denscharger CAI kit. So I can't say for sure how much improvement was due to the plugs, but between the two it sure runs good.
Would I replace the plugs with Iridums again??? Yup, guess I would...
Don't forget the anti-seize
JB