My car is getting 10mpg. It's supposed to get 20mpg. My mechanic took the whole top of the engine off and found a busted gas line. He fixed it, and it's doing the same thing. I have replaced the MAP sensor, TP sensor, spark plugs, thermostat. He said there were no other leaks, the fuel injectors looked ok, the fuel pressure regulator wasn't busted, and there was nothing wrong with the vaccum. Everything shows up as fine on a diagnostic, and an intermittent diagnostic. He claims the O2 sensors are ok as well. Black soot coming out of the exhaust in idle.