Preheat oven to 375 degrees. Grease and flour a 10-inch tube or bundt pan.
For Streusel Filling
Combine 2 tablespoon cake mix, brown sugar, and cinnamon in a medium bowl, stir in pecans.
Combine remaining cake mix, flour, eggs, sour cream, oil, water, and sugar in a bowl. Beat at medium speed with an electric mixer for 2 minutes.
Pour two-thirds of the batter into the pan. Sprinkle streusel filling on top of the batter. Spoon the remaining batter over the filling.
Bake at 375 degrees for 45 to 55 minutes or until the toothpick inserted in center comes out clean.
Cool the cake in the pan for 25 minutes. Invert onto a serving plate and then cool completely.
Combine powdered sugar and milk in a small bowl. Stir until smooth. Drizzle the glaze onto the cake.
You will want to make sure you use a full-fat sour cream. It will taste better than if you use fat-free or low-fat.If you want, you can use walnuts instead of pecans. Just make sure it's finely chopped walnuts.Make sure the cake is completely cooled down before adding the glaze. This will make sure you don't have a soggy mess.