It depends on what year FXT you have. Add info to your signature so it is easier for people to help you.
I didn't search your part number and am assuming it is the BOV recirc hose.
If you have an 06-08 you can use your stock BOV hose.
If you are 04 or earlier you need a STi or 06-08 FXT hose.
If this isn't what you are talking about, provide more info so people don't have to work hard to help you when you don't search.
Sorry, I left that bit unclear.
You will need a BOV and hose from either an 04+ STi or 06-08 FXT.
I don't personally know about the WRX fitment but generally speaking I've found that scubadoober knows his stuff.