I own a 1995 fd3s and I have a street ported 13b engine with a to4r turbo. I am running a stock fuel injector setup but I have a greedy elbow with injector mounts in.
What size injectors should I use.
Were can I get a fuel rail and fittings to use on these injectors

 

if i understand what you're trying to do, then you're going for a 3-stage injector setup, right? well, i can't really help you with choosing the injector sizes, so hopefully someone else would chime in. with 550s and 850s as stock, maybe another set of 850s???

anyway, off the top of my head:

injectors: www.injectorsonline.com

fuel rail: www.atpturbo.com

fittings: www.summitracing.com

however, considering that you're in the UK, maybe you could try your regional forum to find sources more local to you.

hope this helps.