Re: 2005 owners...NGK spark plugs, ITR6F13 or ITR5F13?
The 6F is one step "colder" than the 5F. A colder plug is better if you drive the car hard but is more susceptible to fouling if the car is idled a lot, never sees above 3k RPMs, etc.
Mine came with the 5F too, and I don't see a reason to switch to the new recommendation unless you're getting any knocking in really hot weather on 87 octane and/or drive very aggressively. If you do, switching to the 6F may help a little. The main reason not to switch when replacing plugs on an 04-05 would be if you drive really conservatively and/or idle the car for long periods, because you may see fouling with the 6F that you aren't getting with the 5F.