Nos/Supercharger/Turbo customers usually request One step colder plugs:
Not my words and maybe slightly out of context:
Anytime you run boost, or a high compression engine, you want to use colder spark plugs than stock. Basically you've got a piece of metal sitting in your cylinder that is searingly hot. The right amoutns of Heat + Fuel + Pressure = Combustion.
Now, if that plug is too hot, then it will preignite the fuel too early, and cause that ever so nasty situation called "Detonation" which can lead to your whole engine going KABOOM. And thats a bad thing.