Preheat your oven to 350°F (175°C) and grease or line a muffin tin with paper liners.
In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, salt, and spices (cinnamon, nutmeg, ginger, and cloves). Whisk until well blended.
In a separate bowl, combine the pumpkin puree, vegetable oil, and eggs. Mix together until smooth.
Pour the wet ingredients into the dry ingredients. Gently fold the mixtures together using a silicone spatula or wooden spoon until just combined. Do not overmix; it's okay if a few lumps remain.
If using, fold in the chocolate chips or nuts.
Divide the batter evenly among the 12 muffin cups, filling each about two-thirds full.
Bake in the preheated oven for 20 minutes or until a toothpick inserted into the center of a muffin comes out clean.
Once done, remove from the oven and let the muffins cool in the tin for about 5 minutes before transferring them to a cooling rack to cool completely.
Store the muffins in an airtight container at room temperature for up to 3 days or freeze them for longer storage.