[xlr8or]

You were probably uncovering the jets as mentioned. To check you can try pumping the gas peddle when this happens to get gas out of the accel pumps. If it helps then the jets were sucking air. If it gets worse you may have been sloshing fuel through the vents.

Do you have center hung floats, they can help along with the jet extensions and vent whistles. The side hangars will sometimes get held in the up position by the slosh not allowing more fuel into the bowls effectively starving it on long turns.