well. It depends. A FMIC or rather an intercooler is not a CARB item. However a BOV is one. So a FMIC with the stock BPV should be ok. There where it gets complicated. If you use a non stock intake you will fail. If you use a CARB approved intake again you should be ok.
You will have to take it to the referee and have it certified.
There are threads about that in the local CA forums here and the "other" Impreza club.
Cheers
Nick
PS: you can always put it on and run it. I do not think you can go to the referee on your own but not sure. (meaning an officer can write you up and send you to the referee). Me personally I am not yet ready to cut my bumper for a FMIC. Oh by the way if you have to cut or remove the bumper beam that is ilegal as well.