Riello burner f3-40 smoke smell?

2 years ago I replaced my forced hot air unit and decided to go with a riello f3 40 seris unit. Year one set to warm air furnace specs there was no problem. I did notice a very slight heavy(maybe dust) smell when the circulator turned on after firing up. The odor was there but not objectionable. Year 2 i did a a tune up, new filter, nozzle and exchanger cleaning. After a month of limited operation the combustion chamber carboned up to point of blocking the nozzle. After just cleaning in front of nozzle and firing up the unit i left for the winter. The unit had a blow back maybe a chimney fire. and who knows what else. Before the house frooze i got a technician in he got the unit to run for the rest of winter. The house did get a very strong odor any time the unit ran. I have done the following to this ARCO AIRE unit prior to the upcoming heat season. I took the sheetmetal skin off one side and throughly cleaned blower/exchanger area. There where blower wires in that area that burned and shorted I rewired and rerouted them outside the air exchanger area. I changed the fuel oil filter. I changed the nozzle to sam size but correct angle and flame pattern specs. After doing all that the heating system smell is 98% gone. I feel i am more sensitive now to orginal unit odors of 3 years ago. I would like to get rid those odors if possible. I have done the following: I have taken the back skin off and started the unit to look for heat exchanger leaks. There where none obviously visible. I have leaned the air /fuel mix some as the smoke color looks too orange. It still looks rich to me. I have also noticed some soot from the flue pipe over the top burner. What's might be wrong? furnace exhales with a 5 inch flue , my chimney is 7 so I adapted up? I also have a flue barostat installed, is that necessary with riello intake shut off? thanks for any help

Mike Costanzo....Vermont
September 2008