Not sure what an emptied out cat would do. I assume that would increase exhaust flow, which is the opposite of what I was thinking. But how/why would a thief carefully disassemble the cat, empty it out, and put it back together installed on the car? That just doesn’t make much sense to me. Here people steel cats all the time, but they just cut them off and take the whole thing.
Did the exhaust specialist give you some reason they think the cat has been emptied? Did they do some sort of diagnostic? Usually they look at temp or backpressure at least.
I’d drive it for a while - maybe 50 miles or so - now that you replaced that last o2 sensor and the fuel trims improved. The engine will learn new adaptations and might sort out the rough idle.
Ok so it was a 4 hour job...
Cats have not been emptied, and dont really appear clogged
Once they were dissassembled he poured 1.5 bottles of liqui moly cat cleaner (the type you should connect to the air intake) in each cat and let them sit for 30 mins (he turned them over half time) and reassembled.
Interesting to note that they appeared to have been dissassembled before (bolts were a cocktail) and the right side cat was a bit loose (leaking maybe?)
It smoked like crazy for 15 mins when the car was started
I also poured a bottle of liqui moly cat cleaner (the type that goes into the fuel tank) and half filled the tank.
Lets see if it fixes things