Acceleration problem

[mitiracing]

Hello all,i have one annoying problem that I can not decide.When i starting acceleration around 2000-2500rpm i feel something like a hole for a moment, then took away. I changed the spark plugs,air filters, fuel filters, trottle body synchronization, and TPS synk.. Has anyone had the same problem, it is very nasty when applying gas out of turn.Thanks in advance.A bike is 2000 years whit 24000km completely original.