Preheat the oven to 375 degrees F. Grease a jumbo muffin tin.
In a small mixing bowl combine the flour with the salt, cinnamon, nutmeg, cloves, ginger, baking soda and baking powder and set aside.
In a large mixing bowl beat together the brown sugar, eggs, oil, and vanilla extract until combined. Stir in the pumpkin puree. Use a rubber spatula to stir in half of the buttermilk. Then fold in half of the flour mixture.Repeat: Fold in the other half of the buttermilk followed by the remaining half of the flour mixture. Don't over-stir or the muffins will be dense and heavy. Just fold it in until everything is incorporated (it's okay if a few small lumps remain). Stir in the chocolate chips and pecans.
Spoon the batter into the greased muffin pan, about 3/4 full. (Alternatively you can line the muffin pan with paper liners.)
To make the crumb topping, put all the ingredients in a small mixing bowl. Use your hand to thoroughly combine the mixture, then crumbling it into clumps. Sprinkle the crumb topping over the muffin batter.
For jumbo-sized muffins, bake in an oven preheated to 375 for 30-35 minutes or until a toothpick inserted into the middle comes out clean. For standard-sized muffins bake for about 20 minutes or until a toothpick inserted into the middle comes out clean.Let the muffins cool for a few minutes before removing them from the muffin pan.