My 2009 XTZ started loosing power. It got so bad that in high I thought I would have to push. It had plenty of power until you pushed about 3 in on the throttle and then nothing. We rode it down the highway and it quit pulling around 5000RPM in high
Here is what my dealer found.
1. In nuetral it is suppose to start cutting out at 4500RPm (to keep from blowing motor) Mine was fine
2. AC said that it sounded like the ECU thought it was in nuetral. To check the following. Check the wire that goes from the shifter to the ecu could be loose or broke. (Mine was fine.)
3. If it was not the wire then it had to be the ECU. They sent him a new one installed itand back to full power.
Also have you checked the prefilter behind the drivers seat. Just a thought