Set the oven rack to the center position. Preheat to 350ºF (176ºC).
Lightly grease a 9x5-inch loaf pan with cooking spray or vegetable oil.
In a large bowl, sift flour, cornstarch, baking soda, baking powder, salt, cinnamon, ginger, nutmeg, cloves, and allspice together. Thoroughly mix with a whisk until combined.
In a medium bowl whisk together eggs, granulated sugar, and brown sugar until smooth and pale yellow in color, 1 minute.
Slowly whisk in the vegetable oil into the egg mixture until completely mixed, about 30 seconds.
Whisk in pumpkin, whole milk, sour cream, and vanilla extract into the egg mixture until smooth, about 30 seconds.
Add the egg mixture to the flour mixture. Gently fold the flour mixture until just moistened, making sure to scrape the bottom, with some lumps and flour spots remaining. Do not over mix the batter.
Pour batter into greased pan and smooth top with a spatula.
Bake the pumpkin bread until a toothpick inserted in the center comes out clean or internal temperature reaches 195 to 200ºF (90 to 93ºC), about 50 to 60 minutes. If needed, cover the bread loosely with foil about 45 minutes into cooking to prevent the top from getting too brown.
Cool the bread in a pan for 10 minutes.
Carefully run a knife or small spatula around the sides of the pan, remove the pumpkin bread and transfer to a cooling rack.