Heat oven to 400℉. Prepare a loaf pan by coating with butter, then line with parchment paper. Set aside.
In a medium-sized bowl, combine dry ingredients: flour, cinnamon, ginger, nutmeg, baking powder, salt, and baking soda. Whisk then set aside.
In a large bowl, whisk together sugars, oil, pumpkin puree, eggs, sour cream, and vanilla extract. Fold the dry ingredients into the wet ingredients until just combined.
Divide the batter in half, adding to a medium-sized bowl. Add cocoa powder and chocolate chips to one-half of the batter and mix well to combine.
Add alternating scoops of each batter to the prepared loaf pan. Using a butter knife or wooden skewer, swirl the batters together without combining them fully. Bake until a cake tester inserted comes out clean, about 45 minutes.
Let cool on a wire rack for 10 minutes, then remove from pan and place on wire rack to cool completely. Slice, serve and enjoy!