Preheat oven to 375 degrees F (190 degrees C). Grease and flour a 10 inch tube pan. Sift together flours, soda, baking powder, cinnamon and salt. Set aside.
In a large bowl, combine oil and sugar. Add eggs one at a time and mix well. Add the flour mixture and beat until smooth. Add nuts, yogurt, vanilla and pumpkin and blend until smooth. Pour batter into greased 10 inch tube pan.
Bake at 375 degrees F (190 degrees C) for 1 hour or until a toothpick inserted into the center of cake comes out clean. Cool in pan for 10 minutes, then turn out onto a wire rack and finish cooling. Dust with confectioners sugar before serving.