A friend of mine has an Astra. It came up with error code P14 (exhaust cam advanced). I replaced the camshaft control solenoid, and it was okay fora short while. But then started losing power, stalling and throwing more error codes. So she took it to a dealer workshop. Their diagnosis was "stretched timing belt". I haven't heard of this before. Usually just hear about them snapping and wrecking the engine, or some teeth breaking off, and it slipping out of phase. I guess if the belt became longer, it would be benign at constant speed, but then go out of phase when accelerating?