many people are quick to just blame the metering head on rst's as they have little to no understanding of how it works, first two things i would check are
1, disconnect the fuel pipes from the injectors and put the ends of them into a bottle 1 bottle for each one, crank the engine and make sure they are all delivering fuel instantley
2, remove the fuel return line and make sure it is free of blockages

do these checks then post results