I think it can also be the other way around. Those problems can cause a cat to go bad.Could the problems and symptoms I am having with my Corolla be caused by a restricted or faulty catalytic converter?
If your cat was plugged up, you would have lack of power at highway speeds, especially when trying to pass a truck or other slower vehicle and especially on a slight upwards grade (a slight hill). It would also cause your transmission to operate abnormally (at highway speeds).
Pulling the exhaust to inspect the cat is not a hard job. You'll be able to see right in to the front of the catalytic converter. You won't be able to see the back of the converter without a boroscope, though. You can shine a bright light into the O2 sensor bung hole and look for the light to pass through the catalysts media to the front of the cat. It will look like difused light if it is not plugged up. If it's plugged, you will see only a spec of light here and there through certain of the square holes in the honeycomb media, with most of the holes having no l ight coming through at all.
You can also put a shop vacuum cleaner in reverse and see how well air flows through the cat.
If the cat is not plugged up, it can still be inefficient, needing to be replaced. That's the case with my cat.