well definately go with some stickier tires. beyond that, if your willing to give up some of the cornering ability in favor of more squat and a better launch, along with a softer ride, go with a slightly taller sidewall, softer springs, and zero or positive camber. Also higher gearing wouldnt hurt either, and it would get some of the mileage you lost to the supercharger back.
What springs are you running, because in your videos you seem to have absolutely no squat, and considering youve got 500+ hp thats scary.
How fast have you gotten your Z up to, you say its fast above 80 but im curious how fast youve been, cause the Z isnt known for its high speed stability.
Your Z is beautiful, and was the deciding factor between me looking for a 240z or a newer car. I was on the wire for a couple years and as soon as a saw your videos on taner.net i was sold. I also know of many people who have converted to Zism because of you. so basically im saying good job.