Hi Dan, I don't want to sound supercilious, but I can't see why you had such a problem. It's 5 minutes to get the old one off (undo top 6mm vac hose clip, 25mm bypass hose clip and two 10mm flange bolts) and about 15 tops to install the new one, assuming all the rest of your plumbing is stock.
Admittedly, it is possible to skin your knuckles a bit screwing or undoing the valve cap for correct adjustment once the inter-cooler cover is back on, partly over the top of the
BOV.
Loosening (not undoing) the small Allen bolts in the flange base enable you to turn the
BOV to better align it and avoid fouling other fittings, but they do come already set up for the Mazda (see single dot - Subaru is two dot alignment). Re-tighten them after you get the positioning right.
Anyway, good luck

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