Wow, That’s a lot of things going wrong all at once. I will start with the fluctuations in idle. It sounds like the HFM meter is giving some faults, or the fuel mixture is at one of the limits. The stalling might be caused by a faulty over-voltage protection relay. Some of these things could be an intermittant failure and not show up as a fault on the magic computer. Sometimes the technicians need to use that thing between their ears and listen to the customer complaints instead of relying on a machine to give them the magical cure. A side note: Take the car into the repair shop when the thing is acting up!