RE: air in fuel lines
have you balanced your prop?is the tanksurrounded by foam?sounds like yiou have a vibration that is causing fuel foaming,or you have a pin hole leak somewere.you can check for an air leak by emptying the tank and capping all lines execpt the feed line to the engine then apply vacumn to the fuel feed line,I uae an old fuel bulb and watch to see if it fills with air or stays squashed.if no leaks turn up then it is a foaming problem