[Dr Zoidberg]

The dealer called, the car is done,

a brief summary , I will know more once I speak with the mechanic ,

unrelated,-
they found several codes pointing to a stuck-open thermostat- it was replaced under CPO

related-
They found several codes pointing to a valvetronic issue.
The screeching noise they said came from the valvetronic motor. ( what!! )
after troubleshooting the issue by swapping out the valvetronic motor and sensors, they found a faulty eccentric shaft sensor. and that was causing both the noise and the idle/drivability issues

A couple concerns

I dont understand how this sensor failure could cause the valvetronic motor to squeal /screech like that, but I do understand now why it was not happening under throttle.

I also dont understand that if the motor was screeching that bad , how nothing in the motor was not damaged. As I am guessing the eccentric shaft sensor was telling the motor to go beyond its limits?? no idea ?

Any help with this would be great.