Sounds more like a dealer humming his favorite tune to me!
Oh let us please diagnose it for a fee and since we got now, you are up a tree!

Better to put your money towards an AMM if nothing else but for a spare. The customers before you paid for the one in the mechanics tool box. It called a trail and error diagnosis. We are able to do that ourselves as we have been led out behind the barn once before!

A bad 0-2 does not cause that much of "dramatic" control over the car. If you had low amounts of exhaust coming out the tailpipe, then yes, there would be a loss of power as it would not be breathing. If it is doing that it needs EMS....Emergency Mechanic Services not a sweet talking service manager.
If it was doing all of that would you not have a code for the CEL. You did not mention a CEL on!

Look around for a bad air leak behind the AMM, throttle switch disconnected or the throttle body needs cleaning. It's must be running lean this time.

Phil