To  make  small  adjustments  to  each  unit  make  uniform power  generation in every unit.  Pmax  by  timing  of  fuel  pump(vit  or  by  shims  to  pump  or  cam  floating and readjusting)  Pcomp in ME engines by exh valve timing change.  Pmax- Pcomp not more than 35 bar to avoid piston ring failure. Pi adjusted by fuel index. (But limits are The peak pressure difference can't be more than 3 to 5 for AE And max 10 for ME. Exhaust gas temp diff 40deg C. Fuel  rack  should  not  be  adjusted  more  than  10% Otherwise  we  have  to change the plunger and barrel)    
Marine Engineering exam notes for Seafarers