[jhv48]

Jet extensions and racing floats usually reduce this effect. Basically, when you hit the brakes hard, fuel in the front bowl flows away from the main jet and can uncover it. Also, fuel from the back bowl can slosh forward and up and out of the bowl vent momentarily flooding the engine with raw fuel. Try lowering the back float level and see if that helps. If not, try jet extensions on the front main jet.