on a 400 big block with a stock mechanical pump what should the fuel pressure be around..i am showing on my gauge around 3-4 lbs .. i am thinking the mechanical pump is the reason why my motor want stay running , i put a holley 4 bl 670 street avenger.. not stock motor was rebuilt about 3 notches above stock on the cam .it seams it is staving for gas when i give it gas it is like sucking air. any help would be much appreciated..thanks