I'm not sure where you heard that, but from all the dyno tests we've done on them, on a lot of the more moded cars, they come up with less HP then most of the stock cars, in fact on some of the cars, we lost HP with the iridium vs. platinum ones. For the price, they are not worth the price at all. Believe it or not the ones that I've had best results with are the regular Bosch platinum plugs, which for a set of four are less then $8 at discount auto.

Copper plugs will make a tad more Hp, maybe, but they have to be changed so much more frequently, it's almost not worth the hassle, though if you're big into projects, and keep up on that stuff, I would recomend copper over iridium any day.

Good luck,
Later!