When you popped that injector off with the new nozzle in it and released the handle the pressure dropped waaaaay too quick. So either you have a leaky connection. The plunger in tbe tester isnt flash or the clearance between the new needle and nozzle is too great. Plus what happened to tbe face on the cap where the return rail sits??? That should be dead flat not all bashed up. Alsno never ever use copper washers on tbe return bolts. Should be face to face. They never came from Ford with washers. Flile everthing flat and assemble. Fitting washers gives you 2 more faces to leak and the washers bite into the brass banjos on tbe rail. Ive been rebuilding those injectors for 44 years now so Ive done quite a few thousand of them.

Thanks for the comment, glad you enjoyed 👍🏻