The V8 Owners Forum -

Drill 2 small holes 1/8" to start in the throttle plates on the primaries so you can reset the throttle plates further closed at idle (so they do not uncover the transition slot, remove all casting flash from the boosters and the primary venturies, streamline the primarie throttle plates and shafts, this should make the boosters more sensative and respond better to you cracking the throttle open. Then put a stiffer spring for the secondary air valve so it opens more progressivly when you open the throttle and keeps the velocity through the venturies up. there are further mods in Mr vizard's book that will sort out this problem on this carb.
Mike

just another thought, have you got the acceleration baffel thing in the top of the float chamber that stops the whole carb going lean when you accelerate?
Mike