Don't know if this will help I contacted Magnum about my rsx850i and this was the response;
Thank you for considering Magnum Tuning as a potential source of your online purchase.
There are different engine managements fitted on 850i RSX models. If ECU was integrated on the intake unfortunately none of our fuel programmers would be compatible. We discontinued advertising RSX850i fuel controllers months ago hence this possible issue.
When you have time you can surf through our site to get the scope of everything we offer to your ATV, if ECU is still not integrated on the intake on your model. EVO-Tech Programmable performance chip, featuring Remote controller
deliver 15% extra power – torque relative to the original engine performance and crisp acceleration throughout the RPM range. These fuel controllers trick the ECU thinking the intake air much more cooler, then the ECU will send more fuel for a richer mix besides if the fuel trim is controlled by exhaust oxygen sensor on your ATV, they fool O2 sensor voltage signal to block restrictions developed by the ECU.
Fuel controllers will not override the factory speed-, RPM governor though. This item may work on your RSX.
REVOLUTION PRO-II Programmable REV Limiter Ignition Control Module
is supposed to fully modify ignition timing and RPM/speed limit. As a secondary upgrade it works in conjunction with the fuel controllers.
REV-PRO requires certain some skill for installation.
REV-PRO Installation note
Prior to purchase dismantle your ECU and check whether you are able to remove the silicon seal from inside applied on some models - because you need to access to the factory quartz crystal. The process is not complex but takes a while, can be done with the help of a heat gun and some paint thinner.
Our dyno-proven performance plugs deliver some additional horsepower besides reduce fuel consumption, thanks to the state-of-the-art, 360-degree, round electrode. Their lifespan is 25K miles - 40K Km. In the long run they pay for themselves.
Cold intakes are designed to dramatically reduce intake restriction allowing more air flow to your engine and to create a perfect spiral air flow shape. Both intakes special below improve both horsepower and acceleration in addition they increase fuel efficiency.