Stand alone? For street
F.A.S.T. is pretty easy to tune once you understand what each graph does to your engine. You will need someone to tell you that because the manual does not do a good job of it. It is easy after that.
The unit controls
A/F ratio
timing
cold crank
idle
nitrous activation
nitrous fuel
added fuel for nitrous
logging
IAC controls
auxillary fuel enrichment
My advice would be to pick a seller that has a reputation (good one) selling and running that system. Make sure he understands you need help with a base tune and a good understanding of the system.
What kind of problems are you having with the stock computer? 





J/K could not resist it! 