had the maf replaced on my 00 last year. just went one day driving out from work. car went into limp home mode so i limped to my mates house as it was closer. couldnt get the car above 45, 2500rpm if you tried.
reset the ecu with the secs unit and instantly cel flew up and ther secs confirmed the code as maf failure. got it done under warranty but about £100 from a dealer is about right. if they try and charge you several hundred there trying to get you to replace the whole section and not just the sensor so tell them where to go with that idea.
such a common failure that many subaru websites sell them for that year.
http://www.scoobyworld.co.uk/catalog/index.php?cPath=47_185