Put oven rack in middle position and preheat oven to 350F. Spray muffin cups with non-stick baking spray or use liners.
Whisk together flour, baking powder, baking soda, salt and pumpkin pie spice in a small bowl.
Whisk together pumpkin, oil, eggs, sugar in a large bowl until smooth, then stir in flour mixture just until combined.
Divide batter among muffin cups (each should be about ¾ full)
Bake 30 to 35 minutes, until puffed and golden brown and a wooden pick or skewer inserted into the center of a muffin come out clean.
Cool in pan on a rack 5 minutes, then transfer muffins from pan to rack and cool to warm or room temperature.
