You need the 1:1 because of fuel pressure on one side, and intake pressure on the other. Lets look at it this way. Let's say you have 45 psi of fuel pressure in the fuel rail, and X amount of fuel flow at that 45 psi fuel pressure. Now add 10 psi boost pressure to the other end of the injector(intake side), and now you have reduced the fuel flow from the injector, theoretically, to 35 psi, making up for the 10 psi difference in pressures from the fuel rail to the intake. A 1:1 regulator will raise fuel pressure by 1 psi, for every 1 psi boost, to keep fuel from the injector more consistant. Another example is if lets say you ran large injectors on the stock ecu, and ran 15 psi of fuel pressure, without a boost referenced fuel pressure regulator. Now you run 15 psi boost. In essence, you would have no fuel flow out of the fuel injector, because pressures are even on the fuel rail side of the injector, to the intake side of the injector. Just a little simple physics going on, thats all :)