Carburetor Guru needed!

Okay my 1967 Barracuda 383 install is completed, and the power and torque makes all my B-body swaps boring, but i have a problem. I've rebuilt lots of 1 bbl and 2 bbl carbs and ony a few 4 bbl carbs, so therefore i need some guidance. the car goes like hell feeding the throttle firmly, but if i hammer it to the floor quickly, i get nosedive, pop and maybe a stall. i've set the float level, the float drop, cleaned the carb throughly, prior to putting in the kit with new needle and seats, gaskets, and accelerator pump. could the secondaries be opening to soon? appreciate all suggestions. Thanks Gerry