My cats were rattling terribly just last year, sounded really awful and loud. When I had them removed for new ones I could see why, one huge chunk was lose and rattling away. The noise varied with revs.
Get under there with the engine running maybe you will be able to locate the noise as the cats. If you really want to make sure disconnect the cats, although that would be a pain to do as the drivers side cat is welded to the downpipe. Thanks Audi for another helpful design 'feature'
The stock ones are made using ceramic honeycomb, not very durable.
Last edited by Goran; 18th January 2017 at 09:48 PM.
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