First we need the model along with the type numbers of the engine. You provide the model but abut 100 different versions of this engine.
Second I think you are referring to the breather tube grommets. Those don't affect the carburetor performance much. Now if this engine has a metal gas tank than it likely one of the root causes of the carburetor problems. There is a fuel well that tends to rust out along with the tank itself getting very rusty. Usually this requires replacing the tank. the problem here is that Briggs quit making the tanks or at least they did here in the states.
