I know Mercedes does some test with a cat by pass pipe,on some engines.If it throws codes I don't know.However all my cars first thing I did was ditch the cat.Never had codes,in fact it stopped some.Power loss you may clean your air sensor in intake,behind air box.I have too cleaned oxygen sensors with throotle body spray,and let dry.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt