hey bud
i'm sure lots of people on p-wrx will be telling you not to get the blow off valve, it makes a cool sound but trust me you'll get sick of it after a few weeks and you may get a few backfires as well as running a bit rich. as for the air intake; you can do the full cold air intake setup OR just a better panel filter to start, but many will advise that you get the
ecu re-tuned if you do this, especially if you do the full CAI. so all in all the question is, how much do you want to upgrade the car? if you want to do lots of upgrades, then i would say its best to buy all of the bits you want and get them installed one time, then get your
ecu done to handle all the new bits properly and to avoid running too rich or too lean.