wasnt aware of a wrx ra as well as a wrx sti ra , if this is the case it still doesnt change the fact that an sti engine is different , as said above it has stronger internals and as with the sti ra , closed deck block . if i was putting a new engine in to my sti ra it certainly wouldnt be a non sti engine , To sum it all up the standard wrx engine is inferior to an sti engine and would seem a bit of a shame to put a non sti engine in to an sti .