Bad Fuel Pump??

[gofastsandman]

the most important adjustment in any carb job(rebuild) is the float height adj. i would almost bet the floats are set too low and the pumps cant constently supply enough fuel to run wide open. therefor the engine will run WOT until the fuel level is lowered, then it slows to an rpm that the pump can keep up with. all of this can be caused by the float too low and not opening the needle early enough and the pump is playing catch-up. what a coincidence the carbs. were rebuilt and this problem shows up. just my .02

Coincidence? Check the floats.
Bones is right on the bulb. I had an emergency buy on a Sat. that fell apart in my hand when replacing. Pulled 4-5" of vacuum @ idle.
Cheers,
GFS