Hesitant and shaky under full acceleration

[yellow71]

71 olds 350 rocket, was 2bl, now has 4bl 650 Edelbrock and performer intake, under hard acceleratoin

it skips and misses, although engine sounds like it is revving high, will not accelerate at all, yet under almost heavy accerlation it takes off with no problems. Points, dwell, gaps etc all ok, lots of fuel, starts good, runs good until you step on it, then sucks. Suggestions? thanks