anyrthing that age (V3+) is an erratic time bomb
some go off or never stop running then blow up in your face the day after you sell it!
mine is a '98 GTB approaching 190,000 km and has attended many track days and high boost on occasions, never missed a beat
then others are into threir 2nd rebuild even before 100,000' km etc
good servicing ang thorough check ir required - and I would personally go for a re-built motor with receipts/proof of what went into the 'build'
or buy 03 plus model and not worry for 5+ years about the same problem
this is not a SUBARU specific problem but any performance car of that age