I have tried several carb synchronizers over the years (did a lot of foreign multi carb cars) and never found one that worked as well as a piece of hose and your good ear.
Set the idle air screws the same (1-1/2 turns or whatever is correct for the type)
When the engine is warm, loosen one end of the linkage so the carbs are independent.
Balance the air flow in the carbs with the butterfly screws. When the rpm is correct and the carbs are syncronized (balanced), tighten up the linkage connection. You are done with the syncronizer.
Now adjust the idle air and main jet (if adjustable) one carb at a time.
