To make the crust: Mix the graham cracker crumbs, sugar, and melted butter in a bowl. Using a tablespoon, press this mixture into a 10-inch springform pan, and chill for 30 minutes.
Preheat oven to 350 degrees F. Bake crust for 10 minutes and allow to cool. Butter or spray a pan with vegetable spray.
To make the cheesecake batter: Raise oven temperature to 450 degrees F.
In the bowl of an electric mixer, place cream cheese. Use paddle attachment and beat until smooth. Continue to mix and add sugar and salt. Add the eggs 1 at a time, then add sour cream, flour, and spices. Lower speed and add sweet potato puree. Pour the batter into crust lined pan. Place a baking pan of hot water under cheesecake pan. Bake for 15 minutes at 450 degrees F, then lower temperature to 250 degrees F and bake an additional 1 1/2 hours or until cake center is firm.
For candied pecans: Melt the sugar and cook until temperature reaches 310 degrees F. Stir in nuts until completely coated. Pour onto buttered baking pan. Try to keep the nuts in individual pieces or pulse in food processor for praline effect.
Let the cake cool completely in pan on rack for 30 minutes, then wrap in plastic, still in pan, and refrigerate until completely chilled. Loosen pan sides and remove cheesecake. Carefully slice cake with knife dipped in hot water, then wiped. Garnish with candied pecans.