The three carbs I tried were my 625 AFB, my 625 Street Demon, and the dyno operator's 650 Holley double pumper. The AFB was the worst, the Street Demon was next, and the dyno carb was the best. I since picked up a 600 Holley vacuum secondary. I will probably test both the Street Demon and the Holley in the car. I really like the Street Demon's responsiveness.