Boston to NY would only be a small fraction of a 767's fuel capacity.
Also fuel doesn't burn all at once, just where is has access to air. I haven't seen anything on how the fuel was dispersed in the crash, if most stayed in the tank or was spread out in the building.
Well, if you view the video(s) you might see a considerable ball of fire outside the buildings. That ball of fire is fuel from the jets. It is estimated that both jets had about 10,000 gallons of fuel upon impact. The various fuel tanks were ripped apart (no duh) and the fuel exploded in the impact area as well as flowed down even to the main lobby and below.
Fuel is liquid and then expands to form a gas if it can.... It could to some extent as depicted in the 'fire ball'.
But, look at the picture I posted above. It shows where the other plane bits were found... 51 Park Place is not too far from 45 Park Place where other plane bits were found... I don't think some 'truther' placed the newly found plane bit between the two buildings for some nefarious reason.... It simply was not found during the recovery efforts... I assume atm.