No such legcy model as a BT4, seems like a typo made by whoever registered the car. Its a BL5 model subaru legacy B4, DOHC TURBO, M/T with EJ20Y engine code. 280hp as standard.
When i was insuring mine they didnt have the jap turbo legacy in their system, they only has a BE5 twin turbo listed for 2003, they said its the same. They dont have a clue about the imports. Is it down as a legacy turbo on your insurance?