Is the engine light on?
It the engine light on? You might check over in Bilkes/GSpot/paralell universe, lots of f800 folks there.
Problem is, many things can cause what you describe. A cracked hose, throttle body boot, breather hose etc. can do the same thing. Basically anything that is letting unmetered air in. My wifes K75 had similiar symptoms and it was diagnosed here (quite quickly I might add) as a cracked crankcase breather hose.
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