i don't see why you would have any problems with that. it should work with out any problems besides of course the cross member. i have actually myself thought about using the wrx manifold and up pipe, downpipe to make my install easier. i could just sell my brand new up, and down pipe that i bought off of ebay for an rs and get them but then i have the problem of having to run a 90 degree inlet into the turbo. it makes one part easier which i think would be the better idea.