Personally, unless you have converted to a speed density setup over the factory maf system it is your best bet to go with full recirculating. The air is already metered and if it blows it out then the fueling will be off running rich.
The 07 XT and 08 WRX in the United States both use the EJ255 and the EJ255 was also used in South Africa as well. So it's likely that the your friend's xt and your WRX share the same motor therefore you should be able to directly transfer the BOV. I can't confirm this but it seems likely. XJman's advice about being fully recirculating is important to not however if the tuner can safely tune for it, by all means follow the tuner's instruction.
Thank you, I did however get in touch with GFB and gave the them model number which he has and they have told me that mine uses a different model number. The one he has is a 9003 and mine uses a 9001. So according to them it won't fit.