Cat Efi / Stator?

Check here:
http://www.arcticchat.com/forums/index.php?showforum=125

Read the top pinned threads on the kill switch (actually it's the throttle safety switch most likely is your problem.) If that doesnt' get you going, stator diagnostics testing is covered in the stator thread also pinned at the top.

CHECK ALL THE GROUNDS, found 3 bad ones on my brother inlaws sled causeing much the same thing. AND WOW THE BACK FIRES NOW AND THEN

Ok I know whats happening with your sled had a few in that year span..that did the same thing right out of the crate
What you have is a bad fuel injector clogged most likely or varnished up
Whats happening is your not getting the fuel that it needs to run properly and the excess oil is fouling your plugs
When this happens what I did was remove the fuel rail and remove the injectors and soak them in mineral spirits over night (MAKE SURE YOU REMOVE THE ORINGS)
Let them set over night
Put it all back together should cure the problem
But before you remove the injectors check the fuel pressure with a fuel pressure guage just to make sure its not a fuel pump or filter problem

By what I see from your description I doubt its a stator problem