slowly can you run the engine? Is your fault light on or off?

Couple of things to check: Inlet air plumbing... look for splits in the accordion sections, which can be hidden but let in air that is not measured by the air flow sensor. Diagnostics are smart enough to look at engine rpm and mass flow sensor and figure out that there is a mismatch so I would have thought you would get a fault but possibly not (depending on how big a leak). Worth a check but I am guessing not

If you can almost, but not quite, idle and the car has been idling roughly before this then clean the carbon from around the big butterfly in the inlet. When it's closed it doesn't take much buildup to drastically alter the amount of air getting in. This is a gradual process though so if your problem is sudden and drastic then this isn't it. This does not sound like what you are describing.

When you are running at high rpm not in gear, what happens when you gradually slow the engine? Does it suddenly turn off? Run rough and gradually stop? At what rpm?

"there is a high pitched whine"... at what engine rpm are you trying to shift into gear? Are you shifting into drive? How about if you shift into reverse? Does the engine stall and coast down a bit, like the ignition has been shut off or does it seem to stop suddenly as if it is seized up?