Brushed and vacuumed soot and debris from heat exchanger and flue pipe. Replaced the nozzle, filter, and strainer. Checked electrical connections and safeties. Performed a combustionk test on unit, unit is running at 5.7% O2, 45ppm CO, with zero smoke. Noticed the oil tanks are not leveling out properly. Noticed that the filters had sludge build up, recommend adding oil treatment to help breakup the sludge, also recommend increasing the oil line size coming out of the tank to 1/2” to help with oil flow.