You may have a leaky intake manifold gasket. Also try cleaning the MAS and check the intake bellows for leaks. If the mechanic replaced the camm sensor for this problem get your money back. It will only cause a no start problem. Once the engine starts it's out of the picture. One other thing is the air intake temp sensor. When it's bad it doesn't close and the engine is always sucking in heated air. This very well could be your problem. Take the sensor out and let it sit at room temp. If it's bad the rod will only be sticking out about a 1/4 inch. Should be about 9/16 inch long. You can always jam the air intake so that it's never using heated air.