Preheat oven to 350F. Grease a 9x5" loaf pan and set aside.
Beat together butter and sugar until fluffy in a bowl of a standup mixer. Beat in eggs until smooth. Add the maple syrup. and stir to incorporate.
Whisk together flour, baking soda, cinnamon, ginger, cloves, nutmeg and salt. Add slowly to butter mixture. Add pumpkin and then sour cream. Stir in walnuts.
Bake for 50-60 min. Let cool for 15 min. on a cooling rack and then invert pan and release loaf and let cool completely on a cooling rack.
Nutrition calculation is an estimation only. If you need nutritional calculations for medical reasons, please use a source that you trust.