I just took the fuel tank out of the airplane and found an air leak in the metal tubing of the pressure line from the muffler... Would a leak in the metal tubing inside the fuel tank cause the sputtering while inverted.... I ask because the end of the tubing is open to the top of the tank so that would be an opening also unless the leak which is located in the middle of the tank where the metal tube bends up would be in the fuel most of the time except in when half full and / or inverted... thanks for any info on this problem....