Hey guy I don't know if your still following this tread or not .Anytime you have alot of excess fuel on the muff, its leaking from the exhaust port to the muff .thus it can also cause you a surge from not enough back pressure in the tank .also will effect the needle settings .check to see if its warped ,if so place it on a fine grit sandpaper using a piece of glass and lap it back flat ,then make a gasket for it,see if that helps . BTW if the muff was leaking you will need to readjust all of your settings to regain the power you had plus reliability.Good luck
C.W.