My setup is an Audi A3, VR6. DBW (Bosch throttle body I believe). Responds to the idle correction well, the idle target tracks within 50 rpm of whatever I set it to providing the airflow table has appropriate values for the RPM. I don’t have any Subaru experience. All VW/Audi stuff for me. I can put my map up if you want to take a look…it’s not apples to apples…but might help narrow down what the Subaru needs to get it under control
One of my more recent maps can be found here actually
I was working through torque table stuff …but idle was all set by this point