now if you are planning on running juice then you might want to run one step colder plugs to reduce detonation from the juice. If you are needing to change plugs because yours is toast then going to a step up like the iridiums is fine just pickup the IX series and maybe 1 step colder if you run boost or juice.

I don't want you to waste money thinking iridiums will throw you back in your seat versus stock, if anything your response time and idle will be slightly improved but your power and tq will probably stay the same. only change them if stock are crapping out or you want to run juice.