Performed a heating pm on an oil boiler. Brushed and vacuumed. Replaced the oil filter, nozzle and strainer. Started and checked the safeties. Performed a combustion test. 10.4% o2, 1ppm, 0 smoke, 78.9% efficient System is operating properly. There are (2) Hi-vents that have corrosion on the top of them from a previous leak. Recommend replacing them.