I have a 08 king I has now started back firing and seems to be low on power.
can,t find a problem the computer says everything is OK. changed plug and fuel pressure seems to be good.
Could possibly be a dirty injector.
I would also clean,dry and put dielectric grease on every connection and electrical plug on your quad.
One other thing that just entered my mind while typing is, how are your valves? I know very seldom that the valves need to be adjusted, but it might be worth looking into.
Put dielectric on everything last year and checked the valves about 600 km back. Don't seem to hear any noise that would indicate valves. Tried draining the fuel and putting new in case I got some bad gas but didn't seem to make a difference. Haven't had a chance to pull injector or anything else yet.
I finally got a chance to go through things and found that the fuel injector has a screen in the top of it. The screen was dirty I cleaned the screen and everything seems to run great.