Line a 9-inch deep-dish pie plate with pastry; trim and flute edges. In a small bowl, combine ¼ cup sugar, pecans and cinnamon; sprinkle evenly into pastry shell. Set aside.
In a large bowl, combine the eggs, sweet potatoes, buttermilk, butter, syrup, maple flavoring, cloves and remaining sugar. Pour over pecan layer.
Bake at 350 degrees for 60–70 minutes or until a knife inserted near the center comes out clean. Cover edges with foil during the last 15 minutes to prevent overbrowning if necessary. Cool on wire rack.
For sauce, in a small heavy skillet, melt butter. Add pecans; cook over medium heat until toasted, about 4 minutes. Add the sugar, syrup and maple flavoring; cook and stir for 2–4 minutes or until sugar is dissolved. Remove from the heat; stir in sour cream. Serve with pie.