Preheat oven to 350 degrees. Coat the cups of a muffin tin with cooking spray; set aside. In a large bowl, whisk together the flour, butter, sour cream,sugar and vanilla.Gently fold in the peaches.Divide the batter evenly among the prepared muffin cups. Bake for 30-35 minutes or until golden and a toothpick inserted in the center of a muffin comes out clean. Let muffins cool in pan for 10 minutes. Serve immediately or tranfer to a wire rack to cool completely.