93 Phazer II ST will not rev past 6000 rpm

Hey fellow snowmobilers. I am trying to trouble shoot this problem. Just wondering if anyone has had this problem. It idels great and has great low end power and will rev great up to about 6,500 or so then it feels like it's missing. I did notice the gauge lights are dimmer and the tail running light is not working and at one point the headlight was slow to come on. I tried a different stator but that did not fix it. CDI box or ignition coil or voltage regulator i am thinking? Any guests before i spend money on one or the other?

Thanks

93 Phazer II ST will not rev past 6000 rpm