DOHC 16-valve turbo. Originally designed for the North American Impreza STI in 2004 with AVCS and DBW. The same shortblock as EJ255 except the EJ255 has a different domed piston vs the EJ257. The heads also have different components. Subaru of America designates the same part numbers for an EJ255 shortblock, and EJ257 shortblock with the exception of the pistons.
US Market Impreza WRX STi MY04~MY07 (300 hp, 293 hp (New SAE standard))
US Market Impreza WRX STI MY08~MY10 (305 hp (New SAE standard))
US Market Subaru Legacy/Subaru Outback MY05~MY06
Now that's thinking out of the boxer
fyi all 05 + legacy's have built in code reader