Preheat your oven to 375 degrees Fahrenheit. Prepare a 12-cup muffin pan by lining it with muffin papers.

For the Streusel Topping:

Combine flour, brown sugar, white sugar, and cinnamon in a small bowl, ensuring there are no lumps.

Stir in melted butter until the mixture forms crumbles resembling damp sand. Set aside.

For the Muffins:

In a separate bowl, whisk together flour, pumpkin pie spice, cinnamon, baking powder, baking soda, and salt until well combined.

In a large bowl, whisk together oil, brown sugar, white sugar, eggs, vanilla, sour cream, and pumpkin puree until smooth.

Gradually add the dry ingredients to the wet ingredients, whisking until no lumps remain.

Spoon the batter evenly into the prepared muffin pan, filling each cavity about 3/4 full.

Sprinkle or crumble the streusel topping over each muffin, ensuring it covers evenly and generously.

Bake in the preheated oven for approximately 25 minutes (checking around 22 minutes), or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the pan for at least 10 minutes before carefully transferring them to a wire rack to cool completely.