Your rail pressure it too low and your going lean due to boost restricting the injector flow. Talk to Rob, I have my rail pressure determined by the boost and checked by the zytronic computer. Iam using a fuel pressure regulator on the air side of the manifold to give me a pressure signal that goes up one psi per psi boost AFTER hitting a start point that I have set. The extra fuel pressure regulator that Iam using is sending a modest signal ( air pressure ) to the fuel regulator to up its setting. Like 60 at idle and 70 over 15 psi boost, with a start at 5psi in this example.

The boost is retarding fuel flow in the injector, by pushing back against the incoming fuel. At idle your 60 psi rail is giving over 60 psi differential. At 20 psi boost, your getting an EFFECTIVE 40 psi fuel rail difference, thus the leaning out of the engine, even at max injector duration.

Woody