it sounds like your clunk may have come off. if you rotate the plane and what not the fuel will shift becuase it is liquid. the clunk weighs enough to bent the tube to wherever it needs to go, but if it came off, the tube is somewhat rigid and it may be sucking air that way. it is also possible that your pickup line has come off, which is why it sucks air when it is turned. check it for us.
cheers