absolute waste of money.
you can have iridum plugs, titanium plugs, uranimum tipped plugs or even kryptonite tipped plugs and there will be not one hp to gain from it.
the simple matter is that if it makes a spark under cylinder pressures then that is all that counts. once the spark starts the flame kernal spreads and the combustion process is complete.
for what it is worth, the turbo guys and us nitrous snorters use bone stock NGK cr9e or cr10e plugs with no problems whatsoever.
the only advantage to iridium plugs is that they last longer. however iridium plugs can cause problems in performance applications where severe tempratures can cause the extended electrode strap to become a glowing peice of metal that can cause preignition problems.
a few years ago splitfire released it plug and claimed more hp and better gas milage. we took several performace plugs and stuck them in a kz1000 drag bike and dynoed the bike with every single plug we could find including splitfires. not one plug gave the bike any measurable hp increase. conclusion: the $1.99 NGK B9ES performed just as good at the $5.99 splitfire or any other super spark plug.