FYI: Advance has the NGK bkr7eix #2667 iridium 1 step colder plugs for $6.95/plug for the WRX. The Denso's are $12.99/plug at Autozone. Is it worth it? prob not; so I went with the NGK's
iridium is not worth it. after that "special coating" stuff wears off you just have an easy to foul spark plug, i use v-power copper, one step colder, you can get them at advance for like $4 each. they don't last quite as long as stock but they are very hard to foul
NGK 3330s work in just about every car I can think of, Honda toyotas subarus. They are less than 2 dollars a plug and you can make almost a thousand horsepower in a supra with them.