It depends on the failure mode of the cat, ie, random luck
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In my case a smaller corner piece was trapped further down the exhaust acting like a rattle powered by exhaust pulses. Therefore like a musical instrument it rattled at higher pitch as throttle increased and became louder. Therefore going back on what I said earlier removing the cats may not stop the noise. If the same thing has happened to your 8 the mechanic may have to fish around in the exhaust to remove the offending piece of cat.