i just got my evader st back from hobby services repair shop. my car was under warranty and they fixed things that were not even under warranty, now thats good customer service. i broke the engine in with no problems and it runs great. u will have some air bubbles in the fuel line no matter what. if you have alot of bubbles than u likely have a leak, the backplate gasket , head gasket, or carb o-ring, but before i would start ordering all these gaskets i would take the head off and pull the sleeve out and look and see if their is a copper looking ring around the inside of the sleeve were it has wore through the finish , if u do than it is time for a rebuild.