I searched on here and could not find a scrap of knowledge about these so went ahead and bought them anyway just to see if they would fit into a classic phase 1 impreza. What I have is a perrin parallel fuel rail with a set of side feed 794cc injectors from a very recent US sti (yes they are side feed injectors and only certain US sti's are fitted with them, I think the latest ones but not sure how far back they go)

From what I can make out the injectors are phase 2 classic compatible.
here are the pics:









I cant get the injectors out as the bolts are real tight holding them in and I've already smoothed out the grooves on one of the heads trying.
I've also held up a phase 1 injector in the last pic for reference.
I have measured the distance from injector to injector on the rail and its 11cm, the same as on my phase 1 manifold so that should be a fit. Having not ever taken the fuel rail off before does it look like this will be a direct fit to a phase 1 manifold?

 

heres what the injectors look like out of the rail:
Perrin Side Feed Fuel Injectors Subaru STI 04-07

Phase 2 from what I gather.

 

That rail will not bolt onto a Phase 1 manifold. The bolt-holes in the rail body are too far apart. Off the top of my head the OEM rail holes have 33mm between centres, it may be the picture but they look much further apart on the rails above.

 

Yes your spot on with that, the actual bolt holes are in completely the wrong place, goint to need to modify them to fit but cant see that being a major issue. The main concern I have is will the bottom of the rails(ie where the injectors poke out through) actually fit into a phase 1 manifold?

 

There should be about 113mm between centres of the injectors. There's no reason why they should have changed the spacing for the USDM STi so i'd expect them to be ok.

The botom of the injector bucket looks too small however. OEM rail buckets are 20mm at their lowest/thinnest point. Those look closer to 12-15mm.

I'm sure they could be made to fit with a little ingenuity.