And,why do you need a tune?
I am assuming you are referring to a tune(software,possibly on a dyno etc).
What mods have you done on your car(intake,exhaust etc)?
Are all the mods that you have planned completed?
No sense the expense of a tune until you are done.
What area of the country do you live?
Any shops that are Z specialty in your area?
Are you tech qualified to handle mailed to you software?
IMO, take the car to a well known Z shop for a on the dyno tune.
In the S. East, Z1 Motorsports is one of the best.