Pull the codes when your CEL comes back. It will come back if it's running this poorly. I would have immediately guessed the primary o2 sensor, but it sounds like they did too and replaced it. I'm surprised the AFR sensor went bad, but it would cause similar problems. There is a whole host of things that could cause this and cause the car to go into limp mode. I would check spark plugs and for any air leaks pre-turbo side. Unmetered air would make it go crazy.
To quickly reset the ECU, remove the negative battery terminal, secure it, set up on the brake pedal for ~10 sec to discharge any left in the system. Then reconnect the negative battery terminal. Does the car idle OK? Does it immediately drive like crap after a reset? Or only when the CEL kicks in?
A well lit photo of your engine bay should allow us to tell you if it has been messed with others may miss.
"We live for a good time, not a long time."
RIP Colin McRae