2009 sportsman 850XP losing power

On last ride throttle became unresponsive when letting off of throttle after running 3500+ rpm. Typically when back pressure was occurring from slowing down the throttle was unresponsive until the ATV came to almost a stop and idle. This continued for first hour or two of ride. After that the problem went away. Not sure if pressure related from fuel pump or a sensor in throttle body.

Any help or thoughts?

Thanks!