XMR 650 motor fail and poor

Hello friends.
I have a XMR 650 with the following problem.
The acceleration it is only 7000 RPM and cuts, while any other reaches 8000rpm and then cut, it has a failure like you are poor, low on fuel, the dealership has changed all sensors, spark plugs, fuel pump, cables spark plugs, cylinder heads, battery, ignition coil, but continues as were poor, and still does not walk the few bursts .Please help me. grateful