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I don't know if things have changed on newer cars but the IAM is more important. Fine learning and feedback are localized responses. When they accumulate under certain conditions significantly enough they cause the global response with IAM which pulls back timing everywhere. The car is safe but it tries to add timing advance back until it hits enough trouble again. I will ignore little corrections but like to see the IAM maxed. Per the message from Cobb it sounds like these expectations have changed with them at least, but I doubt the overall knock control strategy has changed.

RomRaider • View topic - Subaru's knock control strategy explained

The main culprit for ill adjusted cars in the past has been a dirty MAF or a leak letting in air after the MAF in the high vacuum area of the intake leading to the turbo. Bad gas should pass - otherwise you are stuck with what you have available. I've chased gas before and it isn't worth it. Octane booster - no way can you sustain that. Look for a mechanical fix or get a tune that manages to deal with the knock better.

Per the girlfriend, I had one guy I flashed stage II as a favor (he was running around with a downpipe but it was a bugeye so not too bad) and he had knock. So I went with him for a log and ended up just teaching him not to go up hills in 5th. That will do your IAM in.
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