In a small bowl, whisk together flour, baking soda, pumpkin pie spice, and salt. Set aside.
In a large bowl, combine granulated and brown sugars, egg, vegetable oil, and pumpkin puree. Whisk until smooth.
Switch to a wooden spoon, and add the flour mixture to the wet ingredients. Stir until just combined.
Divide the batter between the prepared cupcake cups, filling about 3/4 of the way full.
Drop streusel over the batter, dividing it equally between the muffins. If the streusel pieces are too large, gently break them up. If they're too small, smash them together to form larger crumbs.
Bake muffins in the center of the oven for 8 minutes before dropping the temperature to 350°F. Bake for an additional 8 to 12 minutes, until a toothpick inserted into the center of the muffins comes out clean or with just a few crumbs.
Cool muffins in the tin for 10 minutes and then transfer to a cooling rack.