750 Eddy Carb issues

Question for anyone who can give me a good answer. I have a 750 Edelbrock on my 340 and it has been giving me problems lately where I cannot get it to idle consistantly. It sounds as if it is sucking air. Under acceleration the car runs great. Changed everything that has to do with vacuum , replaced the 2 caps on the front of the carb, new PVC, new Carb gasket, put on a new fuel regulator with 6 psi, checked the tubular fuel filter, etc.. and still will not idle consistantly. Since the carb is 14 years old and has never been rebuilt I took the carb to a very established engine builder and when he was tearing it down he noticed a few of the Metering Rods were broke. Now how do these break? The carb since I have had it has never been apart. This really confuses me...