(1) This is probably the first thing you should look at. The Ignition Advance Multiplier (IAM) gives you abroad idea of the health of motor - as it relates to significant instances of knock. To understand how IAM works you need to take into consideration how Subaru configures the ignition timing on our cars.
Total timing "available" = Base timing table + Knock correction advance table
This is primarily done to provide a safety mechanism for your car. Your base timing should, in principle, be a conservative timing map which can be reverted to in instances of mechanical failure (safe mode so to speak). The advance table is timing that will be added to the car in instances of no knock.
Essentially, IAM dictates how much advance timing will be added across the entire RPM/Load range of your base timing table. For 16 bit Subaru ECU, the maximum IAM will be 16. For 32 Bit ECUS the maximum IAM value is 1.
So assuming that there are no instances of FLKC (we will get to this), If your IAM is 16/1 then your car will be seeing the full allocation of timing (Base+Advance). If your ECU detects multiple instances of knock across the RPM/Load ranges which it cannot control for individually, then it will start to decrease your IAM value until the knock is no longer present. This effectively reduces the amount of advance timing that is applied to your base map. The lower the IAM value, the less advance timing is being applied - signaling increasing widespread knock.
So essentially, a 16/1 IAM means that the ECU is not experiencing widespread knock which it cannot control for.
