As I understand it the x piece and associated pipework is part of the air correction system, which gives a finer adjustment to the air/fuel mixture. I don't know if this would affect the fuel oveflow but in any case it should be an easy fix if only to eliminate that if its not the problem. I would also check for a stuck or badly adjusted float valve, ultimately thats what affects the amount of fuel entering the carb. There are many wiser than me on here, that may be able to give a better answer, but thats were I would start. Good luck!