I spoke with Ryan @ RVS Performance months back when the Ace 900 re-flash was in the works.
I asked about Z8 re flash and he said waaaaay on the back burner due to lack of time and more demand on Polaris,Can Am

Well, I called him Monday to beg....plead...,whine ...cry....how may orders do you need... what would it take ...speech , ....... and Ryan said
Funny you should ask, its in the works to get with a Z owner near his shop MN to get the Z800 on the Dyno and see if he can unlock any Chinese secrets and the beast within!
If the Z owner is on this forum a BIG thanks and please SPEAK UP and chime in with updates.

ya all read Info on the ACE 900 re-flash below,

Building on the success of our Ranger ECU tunes, RVS Performance, working along with Evolution Powersports, has released its long anticipated ACE 900 ReFlashes. We flash your ECU to our own custom tune. Huge horsepower gains have been realized through timing, fueling and torque limit modifications. We also build additional safety into our tune by lowering the fan on temperature by 20 deg F. The OEM fan on temperature is is too high (well over 200 deg F). In addition the fan on/off temperatures can be set for each customer depending upon where they live and the conditions typically ridden in. Other great features are added and/or changed to enhance the drivability and fun factor of the vehicle. We have brought our vast experience to the SXS market to extract the most performance from the Ranger/RZR 900/1000 engines as possible. Your ecu must be sent to our shop for reprogramming - otherwise, pre flashed ECU's can be purchased outright for additional cost. With this option, there is no need to send us your ECU. HP gains from 25-40HP depending on tuning stage and supporting mods.

Rev Limiters raised to 8500 for both high and low gear
100% Throttle opening vs. factory 50% limitation
Improved throttle response in all modes (E-Gas Settings Improved)
Improved ignition timing advance optimized for 91 Octane for maximum power
Fueling adjusted for aftermarket components (intakes, exhausts and cat deletes) for optimal Air/Fuel Ratios
No need to run a "piggyback" fuel controller with our reflash for most bolt on mods (You are responsibe to make sure your mods are compatible with our programming - Most aftermarket companies' exhausts adn intakes are compatible with our programming)
Torque Limiters removed ("Shaft Saver delete") for a much more responsive and fun vehicle
Cooling fan on temperature is lowered by 20 Deg F, but can be set to whatever temperature the customer wants
Speed Limiter Removed

Please don't blast Ryan with calls and questions, he said its a process and will keep us updated.

He's VERY knowledgeable in regards to clutching and other performance mods.  I see his name on RZR groups daily it seems and just actually received some help from him last weekend when I installed a QSC clutch kit.  He sells these kits through RVS, but I bought mine used from a local guy who upgraded to a new primary altogether.  He was more than willing to help me get the weights correct even with me not buying directly through him.

Kudos to good service.