In large bowl, mix 4 cups flour, the baking soda and 1 teaspoon salt. In another large bowl, beat eggs with electric mixer on medium speed about 2 minutes or until frothy. Add 2 cups granulated sugar and the oil; beat until creamy. Add sour cream, lemon peel, 2 tablespoons lemon juice, the lemon extract and vanilla; mix well. Stir in flour mixture just until blended. Fill muffin cups 3/4 full. Divide crumb topping evenly over batter in each muffin cup.