As I get more into Virginia flakes and their blends, I notice that they seem to burn more slowly than burley blends. Sir Walter and PA, for instance, smoke more "eagerly" and produce quite a bit more smoke, given the same puffing rate and same size pipe bowl, than the Virginias do. Of course the cuts are different. The Virginias I've been trying, the Luxury Twist Flake and the Superior Navy Flake, are, well, flakes, whereas the SWR and PA are ready-rubbed. Is it the cut that makes the different burn rate, or the kind of tobacco, or both? Or neither?