The AEM will not control the Subaru AVCS. It has no ability to read the cam sensors to locate the Cams and adjust duty cycle. Its a closed loop system. The Hydra blindly pulses the cams but its a crap shoot as to where the cams actualy are.. You or the hydra has no idea and the left and right banks are independant so you have an imbalance.
The two best options are Utec with Speed density over Stock ecu or the LINK G3 plugin.
Clark