So, I was reading the AEM EMS WRX application notes ...
... and I noticed this which might be of use to someone with a Hydra looking for a simple solution to this (I know this has been discussed before):
The MAF (mass air flow) sensor can be removed to help eradicate intake air restriction as the base map uses the factory MAP sensor for engine load detection. However, the WRX/92X uses a 5 Volt-Type MAF sensor that, by design, includes the IAT (intake air temperature) sensor as one-piece. If air temperature corrections are needed, AEM has an IAT Sensor Kit (P/N 30-2010), which comes complete with the sensor, wire connector, and an aluminum weld-in bung.
Yes, I know. Blasphemy.