I contacted Perrin stated the inlet for the 08+ WRX is the same for 2005-2009 Legacy GT. Perrin redesigned the inlet for the Legacy which is now the same one for the 08+ WRX. However from what I've researched (and what you mentioned) later model Legacys (07-09) have different BPV hose locations due to an air compressor IIRC. Because the factroy BPV hose on my 05 won't reach the BPV spigot on the Perrin inlet and there is some other hoses, wires, bracket in the way. It's been a nightmare and I don't have a car until I figure how to make it work or find a suitable replacemnt. The factroy inlet was garbage and really not keen on using something that falls about at the turbo.
I may take photos and do thorough walk-through if I get this too work. Because Perrin does not provide instructions for the Legacy.
My hands hurt.