When you start cold how does it run? Do you get a fast idle for a minute or so while it warms up? It should slow to normal within a few minutes. Does it run smooth then act roughly after it is warm? If so then you have a lean fuel condition. That would point to a vacuum leak. I would be sure all vacuum hoses are good before even looking at the Cat.
It looks like previous years you were very close to a fail. One you were at the limit exactly on HC. That leads me to believe this issue has been going on for a while. You just noticed now because it got worse. Driving it that way would do the Cat in. It is possible your Cat has been on the way out for a while causing the high readings. It is also possible that driving the car with it not running well killed the Cat. If it is the latter you need to address both issues. If you get a new cat and it still runs funny it wont last long.
It looks to me like you have a lean mixture. Low CO and high HC points to a lean fuel ratio.
That metal hose is a heat riser. It should connect to the bottom of the air cleaner. It looks broken. That wont cause emission trouble. Its part of the warmup cycle and opens a valve on the air cleaner for fresh air I believe. See if you can find where it goes under the air cleaner. You can get a new riser easily from a hardware store. It looks like foil right. My old Nissan had its heat riser off for years. I really doubt that is your issue, but it could cause a fail for the visual inspection part of the smog test.

__________________

Chris
84 280sl
82 300d euro