What I took away from the rep's advice was that you should close up the gap and go colder than the recommended plug on a "modified" engine.
Modification was described as ANY performance-oriented upgrade ... even a cold-air kit for example.
How much colde heat ranger? How much to shorten the gap?
I'll leave that to the tech guys for their input, but I suppose the real-life answer would lie in proper "reading" of your plugs?