Took car to smog station - failed - indicated fuel mixture sensor and fuel cap needed to be replaced. Took car to mechcanic had engine diagnostic done - also indicated fuel misture senor needed to be replaced but did not find anything wrong with the fuel cap. But now indicated the Catalytic Converter (CC) needed to be replace. I am concern that the smog station did not indicate the CC was bad and even when the engine diagnoss was done [at the mechcanic's shop] there was no mention about the CC being bad. After the sensor was pull in the mechcanic now states the CC is bad. Can this be true or am I being played just to get more money out of me? The car has always been maintained in excellent shape.