I added 3 teaspoons of pumpkin pie spice to the dry ingredients, and substituted Greek yogurt for the sour cream. The large quantity of baking soda worried me, and the batter tasted sour. I was afraid the baking soda measurement may have been a misprint. However, I followed the recipe and the muffins turned out nicely, but not as moist as I expected. I might try a different recipe next time.