You need to check your idle vacumn to determine which power valve you need, manifold vacumn holds the valve closed, not enough allows the valve to open and enrich the mixture. Usually a good rule of thumb is to check your idle vac and if it is, say 10", you would use a power valve marked 5 or 5.5. Since the carbs were rebuilt, I would also check the idle mixture screws on the end carbs, they could be open too much and be contributing to the overich idle. About 1/2 turn out from seated is a good start.