first, I'll say you need to search and read up on threads on here. Not just b/c it will answer most of your questions, but also cause you will gain a lot of knowledge about your Z as well.
that said, only UpRev currently supports tuning for our car
afaik, Cobb used to but stopped.
You're in South FL right? I'd go to HP Logic and have Jack Cecil tune your car, he did ours, was worth the 3 hr drive, he's very very good.