As it has already been mentioned vagcom does NOT work witch CAN bus ECUs. That means it doesn't work for 2006+ Subaru ECUs.
As for flashing 02-07 WRX. Connect the green test connector, connect the flash jumper (get it from tactrix or make it yourself). Then you must connect pins 16 and 11 in the OBDII port. That will get 12V to ECU for flashing. If you have a good battery you'll get a high voltage warning. Just turn the rear window defroster on, it will drop to required levels.