I have a tower 75 and gms 46. The 75 has been trouble free for 10 flights. Then last time out. It started giving me problems. It runs fine on the ground with the nose in the air and flat. But when nose down the fuel line gets air bubbles in it. Then when I bringing the nose back to horizontal it appears that the fuel flows back into the tank. This has caused several dead sticks. I have replaced all fuel lines with no luck. As for the 46 it's new and has simular problem from day one.