Preheat the oven to 350°F. Brush 12 jumbo muffin tins (each with a 1-cup capacity) with oil; set aside.
Whisk the flours, baking powder, pumpkin pie spice, and baking soda in a medium-size bowl. Whisk together the oil, pumpkin puree, yogurt, eggs, and 1 cup of the sugar in another large bowl. Add 1 cup of the walnuts and the reserved dry ingredients. Mix just until moistened. (Do not over-mix).
Divide evenly and spoon the batter into the muffin tins. Sprinkle the tops with the remaining walnuts and sugar. Bake for 35–40 minutes, or until a toothpick inserted in the center of a muffin comes out clean. Let the muffins cool for 5 minutes in the pan.
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