double carb setup installed (looking for advice)

just got the double carb intake installed, seems to be running fine but when i go, i can accelerate and up shift. but coasting it will hold the rpm and it wont downshift, i can kick the pedal and every once in a while it will mellow out, but the return springs seem to be fine and the throttle dont stick im not really sure whats up. was wondering if sombody has advice or if theres
a obvious problem goin on