My Holley 4160 600 cfm carb started leaking out one of the dime sized plugs on the fuel bowl. Called holley and got a replacement bowl. And rebuild kit. I did not rebuild the carb Just used Bowl gaskets, power valve, needle and seats, accel. pump. Carb was perfect before leak. Problem now is it runs way to rich, black smoke out tail pipe. Rechecked float level and perfect. Adjusting idle mixture screw does nothing. What am i missing here? These bowls are so easy to replace i didn't even take the carb off the intake manifold. I did both primary and secondary bowls.