It sounds like you have a fuel starvation problem. Possibly a seized fuel pump or even water in the fuel tank.
I think this has been going on for quite some time now and it may have set several fault codes like misfires in the past. That's probably why the previous owner replaced the coil pack, but that didn't cure it.
Because of these problems the cat has died and I think this is the reason why the car was sold.

Measure fuel pressure and/or fuel flow to start with.
Do NOT replace the cat before the engine is running perfectly, otherwise the new cat will be damaged as well.

Any chance of returning this vehicle and getting your money back? Because I also saw a post about problems with the Traction Control/Abs.
Or do you want to keep the car? Then get a trained mechanic to do a thorough diagnostic on it, not just the engine, but all other systems (Abs, Airbag, etc.) as well.