In my experience, you will want to adjust the "Knock Threshold Weighting Factor" tables as well as the "Knock Threshold Level Final Limit (Max)" value. For the 2011 WRX, the former tables are Per Cylinder, so there are four. Here is the stock "Knock Threshold Weighting Factor" for Cylinder #1:
I have found it is best to modifying them upwards by a percentage in the RPM range you want to reduce sensitivity in. Repeat for Cylinder 2-4, of course. For example, if you wanted knock sensitivity to be reduced above 3200 RPM by a math factor of 5%, I would try modifying them like this, which is a multiplication of 1.05 to the stock values from 3200 and above:
After you finish editing those, you'll want to bump of the "Knock Threshold Level Final Limit (Max)" threshold table to give the max ceiling value the same upwards buffer (same 5% buffer here).
Then reflash and test it out :) In general I have usually only had to increase these tables by 10% to get the system quieted down for built motors. You may find you need smaller or larger.
- Lance Lucas