I remember reading in the manual that 45k is for turbo motors and 100k is for non-turbo motors.
I changed mine at 53k and they looked disgusting.
If you have a tune, you should change them even sooner.
edit: found the pic i took. look at my 53k plug, notice how the gap has grown significantly vs. the new plug.
Last edited by TheBurro; 11-09-2012 at 02:19 PM.