Preheat the oven to 425°F. Line a 12-cup muffin tin with cupcake liners. Combine the flour, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon in a large bowl. Set aside.
In a separate large bowl, combine the granulated sugar, brown sugar, vegetable oil, and sour cream. Whisk these together until the mixture is smooth.
Whisk in the eggs, one at a time, whisking well after each addition. Whisk in the vanilla and the pumpkin until smooth.
As best you can, create a well in the center of the dry ingredients. Pour the wet ingredients into the dry ingredients. Use a rubber spatula or wooden spoon to stir the batter together until everything is just combined.
If you're wanting to make chocolate chip pumpkin muffins, go ahead and stir in the chocolate chips here. If not, continue.
If you want really domed muffin tops, let the batter sit in the bowl for at least 15 minutes before continuing. If you don't care all that much, continue immediately.
Divide batter between the lined muffin cups (this recipe will make about 16 muffins, so you may need more than 1 tray, or just bake 2 separate batches in the same tray).
Bake the muffins at 425°F for 5 minutes. Then reduce the temperature to 350°F and bake for an additional 15 to 17 minutes or until the centers of the muffins spring back slightly when you press on them.
Let the muffins cool in the pan before removing to a wire rack.