Gas and Oil Home Heating Furnaces - Oil Burner Problems

I am having what I think is a problem with my oil furnace. It is a Valiant with a beckett fired oil burner. It was running fine up until a couple of weeks ago, when I noticed black soot particles around the area of the furnace. I opened it up and it was very sooty, so I cleaned it, even though it was just cleaned in October. I took two readings on the furnace (-0.06"WC stack draft reading), (smoke reading of 2). I am not able to get the reading lower than two on smoke no matter how much more air I add. Anyway before I call someone I figured I would check to see if anybody had any ideas.

Thanx:)

Which model boiler do you have? If it is one listed in Beckett's OEM Spec Guide, I can give you the original set up specs.
Valiants are very touchy. Have you checked the end cone on the burner for cracks?