Hi,

In my opinion all you need is an engine in good tune that idles smooth and evenly and it should pass any emission tests.
A catalytic converter doesn’t do anything except help burn up something better that didn’t burn in the first place.
It has to be on there for “looks” to pass the requirements of equipment being in place and no tampering.
The last part gets into play if it’s not passing.
The car may be old enough to be forgiven, as in most states, since the manufacturer probably doesn’t even make replacement components like air pumps or EGR valves or there is a cost limit to have to do it anyway.

Good tune and fresh gasoline with the engine well warmed up usually works.
Volvo did their homework back in the day!

Phil