just has the CEL and code for evap system incorrect purge flow.
ok, this is all together different, maybe.
if they swapped the 97 ECU into the car when they swapped tyhe engine, that could cause a ''incorrect purge flow'' code.
i have done the exact same thing.
there were a few changes with the 98 MY ECU.
i bought a 98 OBW for cheap with a busted timing belt.
after i swapped the engine it would not start.
i finally narrowed it down to the ecu.
it was caked with corrosion due to water damage.
i swapped in the ECU fom my 97 GT and the engine fire right up.
but i had 2 codes.
one for incorrect purge flow, and
one for some sort of traction control issue.
after messing with both codes for a couple of weeks,
i bought a 98 ECU and all is well.
pull back the carpet on the passenger side fire wall,
remove the cover, and read the part number on the ECU.
ECU part numbers for outbacks.
according to www.car-part.com
97 = 22611AD000 and 22611AD001
98 = 22611AD60A and 22611AD62A
there may be others, but these are the first ones i came across for each year.