I use a sport 2k, its been flawless. The thing I see issues with in the MS system is the fine tuning. Getting a car to run is easy, but getting one to run like factory is where all the money is spent. That being said, the S500 is not a good fit, its a lot of work on a Z and not much different from the stock ecu. Id save the money and get the 2k. What are you wanting your engine management to do?