What do the Smoke Flow Advanced settings do? In the Smoke Flow panel there is a section called Smoke Flow Advanced. In this section you can find mapping fields (Size, Offset). Could you explain the nature of these fields and how they impact the fire?
These are mapping adjustments for the emission texture (specified just above them in the panel). Size adjust the scale of the texture coordinates, offset translates the coordinates. Depending on your texture, you may find it useful to animate these to give your flame a more realistic patchy/"licking" appearance.