DEMON CARBS?? wtf is goin on?

i got a new demon 7xx somethin double pumper on my truck .. truck runs great in park. i can get in the 4 barrels and it's is very snappy . as soon as i take it in the street or mud to run it i can roll into it and it will wind up quick till i get 1/2 pedal and it falls on its face unless i pump it then it will run a lil better but i know it's no where near what it should be ... i have a chevy short bed 4wd. its a great runnin motor with a 600 holley on it but it wasn't enough so i changed it . why can't i get into it with out fallin on it's face??? it don't pop or studder just runs outa gas i guess