My engine will idle fine, but when I push the throttle it sputters and clears up, sputters and clears up. Sometimes it sputters real bad, but it always still idles. It's like something catches and it will run back up to full throttle. After a while, it clears up and I can run at full power. I'll be running full throttle, on a plane, it still breaks up and dies back, but never stops running or idling. I had the carbs looked at and adjusted, replaced all the fuel lines and tank. What can I do? 