TO,
Symptoms like that when changing power aren't uncommon.
The likely cause is lean cut or rich cut.
Lean cut is when the throttle is opened quickly, the amount of air entering the engine increases more quickly than the carburetter can supply more fuel, hence fuel/air ratio temporarily drops to an overlean state.
Rich cut can be where an accelerator pump in the carburetter supplies extra fuel to overcome the lean cut, but due to the rate of throttle increase it overdoes the correction.
The usual solution to either problem is to make your power changes more slowly.