Preheat oven to 350. Butter 12cup Bundt pan. Mix 1st 5 ingredients in small bowl. Set nut mixture aside. Sift flour,baking soda,baking powder and salt into medium bowl. Using electric mixer, beat butter and 1 1/2 cup sugar in large bowl until blended. Beat in eggs one at a time. Mix in vanilla. Mix dry ingredients and sour cream alternately into butter mixture in 3 additions. Beat batter on high 1 minute.
Pour 1/3 of batter into prepared pan. Sprinkle with half of nut mixture. Spoon 1/3 of batter over. Sprinkle with remaining nut mixture. Spoon remaining batter over.
Bake cake until tester inserted near center comes out clean, about 1 hour. Cool cake in pan on rack 10 minutes. Cut around pan sides to loosen cake. Turn cake out onto rack and cool 1 hour. Transfer to platter.
Whisk powdered sugar and milk in small bowl until smooth. Drizzle over coffee cake. Serve slightly warm or at room temp. (Can be made 1 day ahead. Cool completely. Wrap in foil and let stand at room temp).