Kawasaki z750 holding back when changing gears?

I have had a full arrow exhaust fitted, along with a power command 5 as well as an airflow filter, the bike has been remapped on a dyno machine, however, when changing up from 2nd gear up to 6th gear, approx 5000rpm, the bike doesnt seem to respond between some gears( random), anyone got any ideas?? could the mapping be wrong, its driving me nuts