You DO have a bad cat. However, since your car is pre-1989, you can adjust your timing. And setting that to 0° will bring the NOx WAY down.
The car will be down on power. The HC and CO will be lower as well.
It's a very easy 'fix' not recommended by the EPA. But you're in Canada eh!
Do what you gotta do!
That simple measure will typically cut the NOx in half.
Tuneup items will all help and really must be all ok to make sure you'er not getting unburnt fuel down to the cat.
Good luck with it.
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Rob Bareiss, New London, CT 86 244, 87 244, 88 744