I have a boroscope so it wouldn't be too difficult to remove an O2 sensor and take a look. I'll put the scanner back on it and watch the O2 sensor readings also and see what we getAhh, the smog test. That sucks.
You can try the bore scope from the upper O2 holes looking down at top side of the cat's honeycomb. I have done it on a Hyundai once but was not happy with the picture quality of the small hand held snap on scope I have.
You might need to drive it more to get a code to pop up. If the misfires refer to one side of the engine than It could be plugged on that side. If you could see the 02 sensors reading and if one was reading different and was on same side as misfire than that would help confirm that it was one of the upper cat's and which one. The lower cat is after they come together and would be more of multiple misfire.
Dirty air filter, cracked bellows on intake tube, intake gasket, throttle body leak, plugged pvc valve, other things to look for.
I would just drop the pipes try to visually inspect/shake maybe even try blowing compressed air both ways see if any material comes out. Then when all else fails, I cut them open from the top side with die grinder pull the material all out then weld them back up like it never happened and use the 02 spacers, if it solves the issue get a new set and weld them back in