K-10, Perhaps I should have said "a manifold referenced fuel pressure regulator". For every pound of boost you put into the manifold you must increase the fuel pressure by the same amount to maintain the same fuel flow. Most or all modern fuel injected engines use a diaphragm type regulator with fuel pressure from the pump on one side and a spring on the other. When the fuel pressure overcomes the spring pressure a valve is lifted off its seat and excess fuel is allowed to return to the tank. The spring tension determine the fuel pressure. The spring side of the regulator is connected to the intake manifold. On a non boosted engine the vacuum in the manifold will cancel some of the spring tension and allow the valve seat to be opened more easily therefore reducing the fuel pressure. They do this to lean out the engine during light load or coasting situations. (high vacuum) This also works in reverse. When you add positive pressure (boost) to the manifold it adds to the spring tension and raises the fuel pressure. Here is a picture of the regulator I am using. It is a "Holley" unit. You can see the diaphragm in the middle and the hose barb on top to attach to the manifold.
