Are there any holes drilled through any of the butterfly plates? If yes, then they all need to be closed up and then go here;
AJ's guide to Transfer Port Synchronization
After that is done, reset the pump linkage, to initiate a stream at the slightest, most gentle throttle-arm movement.A stream not a dribble or a hesitation, and all gas no air!
What the T-port sync attempts to achieve is a synchronization of the transfer ports to what the engine needs.These transfer slots are your main low-speed transitioning circuit. The mixture screws that you can play with, just fine tune it for idling.These transfer slots are the only way to get fuel into the airstream until the airspeed through the boosters starts to pull fuel for the main metering circuit.They have to be timed pretty accurately.
If someone has drilled the plates for a big camshaft, this will totally mess up the sync. If the initial timing is too much, or too little, this may totally mess up the sync. If the butterflies are too far closed then the engine will go immediately lean on tip-in and stumble. If the butterflies are way too far open then idle vacuum may partially dry them up and tip-in will again be lean. And if they are just a little to far exposed then the engine will idle fat. It may just be rough, or it may have a miss, and messing with the mixture screws will give little to no relief.
But if there are no holes in any of the plates then the secondaries need to be closed up just short of sticking, and the brake-booster line clamped shut, the PCV proved correct for the application, and then the T-port sync still has to be performed! When done, un-clamp the booster line, and after a slight sag as the booster comes on line, the idle speed and quality should return to that pre-unclamping.
When all else fails, crank up the float level 1/16" and start capital-A,All, over.
Bolting on a new carb may or may not solve the condition, depending on what is causing the condition. So
the T-port sync is job one! Then cuz the butterflies may find a new setting, the pump-shot needs to be revisited.
Good luck!