That sounds like a 'Sucking Air ' problem , check the rubber inlets between the throttle bodies and head , they might be loose or mis-aligned ?
Also I think it needs a good long hard thrashing , 2000km in one year ?? .
Mine gets thrashed every day riding 40km to and from work in evil Perth traffic , its that or get run off the road by a cage ,,,

Get it out on a nice twisty mountain road and cane it ! , the bike will thank you for that .

But seriously check all air intake seals .

Brian.