Our local dealer said if you take the finger advance_retard adjuster, unbolt it and turn it a full 180 degree (i'm not sure wich way) and lifted the feeder drum so there is 30mm clearance between the end of the finger and the bottom of the header it would feed alot better. They did this to a couple of machines after talking to someone from jd in america and it resulted in an increase in ground speed and no plugs. Hope this will help you