I've been thinking about this recently especially with a pro-tune in mind. It might be a good idea to swap out the OEM plugs for something a bit colder since typically a colder plug will help prevent detonation from the increased heat a motor see's from higher boost levels.
I've gone to a colder plug with my LS motor and will be stepping up to even colder plug once the heads/cam build is done and maybe some nitrous is added into the mix. It doesn't make sense that Subaru's EJ motors would be immune to needing a similar upgrade. People on NASIOC don't really seem to know what to think.