carb breaking up under moderate throttle

[69projectKAOS]

i have a edelbrock performer series 650cfm carb, and i was driving my car the other day before it was tucked away for the winter and when i got on the throttle(heavy) the car sputtered and fell on its face! i lifted off the throttle and eased back on it and it was fine but when i romped on the gas it would break up and lose all power. what do you guys think is wrong? tune? thanks-Dom