Mix vanilla wafer crumbs, margarine and 3 packets Equal sweetener in bottom of 9 inch spring form pan. Reserve 1 tablespoon of crumb mixture. Pat remaining mixture evenly on bottom and 1/2 inch up side of pan. Bake in preheated 350ºF oven until crust is lightly browned, about 8 minutes. Cool on wire rack. Beat cream cheese and 18 packets Equal sweetener in large bowl until fluffy; beat in eggs, egg whites and cornstarch. Mix in sour cream and vanilla until well blended. Pour mixture into crust. Place cheesecake in roasting pan on oven rack, add 1 inch hot water to roasting pan. Bake in preheated 300ºF oven just until set in the center, 45 to 60 minutes. Remove cheesecake from roasting pan, sprinkle with reserved crumbs and return to oven. Turn oven off and let cheesecake cool 3 hours in oven with door ajar. Refrigerate 8 hours or overnight. Remove side of pan; place cheesecake on serving plate. Makes 16 servings.