DO NOT GO POD FILTER!!!!
My car came with one, a Blitz one, so you'd think it was pretty good.. I wondered why it ran rough, even on 98 gas, was slower than other Foresters, etc.. so I put a standard air box back in it, with a second hand filter... It ran smooth as babys ass, and was about 40% faster too... Also sounded nicer I personally think.
So yeah.. Stock airbox = win
Btw.. Standard filters are just as good as any after market one... K&N, Apexi, etc.. Just go buy a standard one to replace the dirty old one.