Dead spot in throttle

[west aussie gas 450]

I've got a 06 450fse an i have a dead spot just after take off? When i'm doing 60kph the bike will rooster tail away from other bikes, but at low speed it sounds if it drops it's gut or sounds flooded.I talked to a fitter in our mine workshop an he said sometimes imported bikes are tuned to certain atmosphere conditions an they can change from one side of australia to the other? I get left behind on take off and i'm copping heaps of over it any help would be great.