There should be a way to ramp fuel supply on the stock pump. I am not a diesel guy but there is always a trick to improving fuel output (like old school Saab 99 turbos - drill a hole in the side of the pressure regulator housing, insert allen key and turn it up, add boost - instant fun) As for turbos, bigger doesn't mean better. Another thing I'm no guru about. It seems the biggest gripe about the stock turbos on 4D55/56 engines is the turbo runs out of chuff before the engine does.