The Supra TT guys seem to start having spark problems at the 500hp area, from the reseach I saw while digging up info about my ignitor. It seems that since the igniter limits dwell (and thus spark energy) they get blowout issues. This was gleaned from a couple thread on the subject, and I'm by no means a JZ expert. So if that info is incorrect, don't sue me.
I consdier any motor in the 400-500+ range to be higher HP range
Maybe I'm jaded since both of my daily beater pickups are 300+.
Like I said though, ONLY the 1995 Avalon got the smart igniter. Far as I know, the other V6's all have "dumb" igniters so it's a non-issue for you guys.
Keep that MS around, hopefully you'll be able to put it to some good use soon