Here’s someone (from 2007) who appears to have had the same or similar problem. Go to the link to check the responses. I haven’t yet.
“Excuse me if I use the wrong terminology...but I have a fuel-oil furnace that white smoke appears through the burner after the burner shuts off and the blower is still running, after about 45 seconds...white smoke starts to come out of these small holes on the burner and fill the basement with white smoke and smell like fuel. ...”
Thanks ETL..checking it out..