worcester 15/19 regular oil boiler,?

my worcester 15/19 regular oil boiler,keeps blowing out black smoke,put new nozzle 0.55 80h,baffles combustion cleaned,air set to 9.25,but when oil pump pressure is set to 130psi boiler runs ok but smoke comes out the vent,have to turn oil pressure down to 90psi to stop smoke,because the boiler 15 years old do i have to allow % allowances with oil pump pressure,over the years i have changed oil pump,solonoid,ignition transformer,and boiler has been well maintained,waiting to have lend of co2 anlyzer,would be greatfull for any advice.