Stir margarine, pecans and brown sugar in bowl until crumbly. Set aside. Beat vanilla, sugar, oil and eggs in mixer bowl until smooth. Add mixture of flour, baking powder, baking soda and salt alternately with sour cream, mixing well after each addition. Layer batter and crumb mixture 1/2 at a time in greased tube pan. Bake at 350° for 50 minutes or until coffee cake tests done.