The fpr watches manifold vacuum, and raises fuel pressure at low manifold vacuum. High vac means low throttle/cruise conditions, and low vacuum means more throttle, needing more fuel. But changing the fuel pressure doesn't make sense to me. The injectors will flow more of course, but the tuning data changes at the same time. So the ecm has to juggle pulse width with the changing pressure. Why not just leave fuel pressure constant, say 50 psi? Is the point of reduced pressure at cruise to save wear on the fuel pump?