Hitachi 470 -5 cutting out

Hello I have a Hitachi 470 -5 isuzu engine cutting out but only when cold it bogs down the engine and cuts out. When the engine is cutting out common rail pressure is around 108mpa @ 1800rpm but dropping when engine under load any idea what the rail pressure should be? when the engine warms up the cutting out stop I must check the rail pressure when its hot and not cutting, out also no fault codes coming up. Thanks