In a large bowl, combine sour cream, sugar, flour, vanilla, salt and egg; stir until blended. Fold in blueberries. Pour into pie shell. Bake at 400° for 30-35 minutes or until bubbly. Remove from the oven. For topping, combine flour and pecans in a small bowl. Cut in butter until mixture resembles coarse crumbs. Sprinkle on top of pie. Return to the oven for 10 minutes. Chill before serving. Keep refrigerated.