Bad cat will cause will throw weird engine codes. The previous bad coils were likely not burning the fuel, if they were even bad, which would contribute to a cat fail. Cats will rattle when they are shot and will be intermittent. Trace the rattle to the source. Bad cat restricts exhaust so engine will only rev so high as the engine can't suck in more air because it isn't getting out.

If they say a coil(s) are shot I would ask that they test the coils by moving a good one around and see if the faults move to other cylinders before buying new coils. I do like to change all the coils when one goes bad--but I am one that never wants to risk losing any amount of performance.

Now that it is missing at idle it should be easier to pinpoint the cause

As per Pezho and Aman

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas