I would really do some good research before you throw a fmic on your wrx. A lot of people i know that own wrx's that have put FMIC's on regret it because there is a lot more lag with the smaller 2.0 engines. Im going to assume that your engine is pretty much stock since you dont have anything on your profile. If thats the case your stock TMIC will do just fine. I plan on upgrading my turbo eventually and i will just get an AVO TMIC or something. I saw one on an 08 sti the other day and its feking huge. Yes, FMICs do cool the air better then a TMIC but most people hate turbo lag lol. I would only recomend a FMIC on a wrx to someone that tracks their car a lot or they have some major engine work done.
As far as your origional post goes, Im pretty damn sure all the FMICed subarus i've seen have short ram intakes or some crazy custome CAI. If you think about it though, a CAI really isnt needed with a FMIC. Anyways, good luck !