P 0282/P 0284 Ford - Testing tool ??? Can I varify injector or wiring?

Question

Replaced #8 injector 3 mo. ago when I the same codes.  Used reman part.  Everything was doing better then ever. Then, same codes.  I am wanting to know if there is a way to isolate the problem, wiring vs injector, before I tear into that monster again.  The E series is a little more of a challenge when compared to the F.  Some small upgrades: pre-fuel marine grade filter/separator w/ site bowl(checked @ each fuel up), pressure kit in regulator, 7 Glow Shift gages including a stepper motor fuel gage with low limit alarm (set @ 50), new Garrett turbo w/ larger compressor and a wicked wheel impeller, and a custom built 225 amp alt tied to an isolator feeding 2-1000 amp conventional and 2-1000 amp deep cycle batteries.