Changed the Cat. and all was good. Does the cat rattle. You could get a Ca emissions Cat. more expensive but also will last longer. It may work better as well. I am not saying for sure it is the Cat but I would bet on it if it were mine.
Actually, I look again and yours are high HC on the 25 mph test and the idle test HC is close to failing as well. My readings were high on the Idle test only.

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Chris
84 280sl
82 300d euro