BMW Repair: BMW 1997 528i 4 doors sedan, tps sensors, oil leaks

Question
Recently I had a used engine installed. The engine was running reach and the misfiring caused the catalytic converter go bad. One of the specialist looked at it and says the Throttle body has to be cleaned for carbon build up and the catalytic converter has to be changed.
Can you put some light on his diagnosis. Should I change just the TPS sensors or the whole throttle body including the sensors. Is there a place which sells the throttle body.
Please help. Thanks.


Answer
I would think there is more to it than just cleaning the throttle body.If the throttle body it that bad than I would repair ANY oil leaks that are noticed,replace the spark plugs,and the cat if nesserary.The opening of the throttle should be about .002.Also need to clean the Idle air control unit as well.