Carb is 3 months old, can that still happen?
if the float is filled or partially, wont the level be high.
not sure what you are trying to say.
Al

I agree with you if you say you've checked the float level while running and its BELOW the hole I beleive you. I'd lower the float down some anyway for good measure and see what happens. If the needle was stuck or sticking or the floats were heavy the dam thing would have fuel pouring out it like 90 going north. Fuel coming out of the boosters can only come from 2 places. #1 the power valve circuit, something is either making the power valve cicuit open up I. E. low vacuum due to high lift cam or a severe vacuum leak or #2 its being pushed through the main jet circuit via a high float level or by being pulled out via venturi vacuum affect from the engine which is not present at an idle.
How high of an idle are you running? what size power valve?
Sometimes I've seen Holley's pull fuel out of the boosters if idled up to high which lowers the vacuum that holds your power valve closed. Try lowering your idle down a bit and see if the problem goes away.
You mentioned you've changed out the power valve several times but did'nt mention if you had tried running a different one it should have 6.5 from the factory,you made need to go with a higher rated one if you have a high lift cam that kills idle vacuum, or just do what most people do and plug it and go up about 4 to 6 jet sizes on the primaries.
Goodluck >< Cp