Bike is most probably set on lean mixture which is why when u try to hard rerv it, it misses and than becomes alright. Was this problem from day 1 or after you got it first tuned? What happens is that most of these so called Ustaad mess up the original settings for carburetor and hence problem like these start. Keep riding it till 3k and after that when you visit ur mechanic for tuning tell him if he changed your fuel settings and ask him to Revert them.