Preheat oven to 350°F. Roll pastry into a 12-inch circle on lightly floured surface. Fit into 9-inch pie plate. Fold edge under and flute edge.
Combine corn syrup, eggs, pecans, butter and vanilla in a medium bowl. Toss ⅔ cup of toffee pieces with flour and stir into pecan mixture. Pour entire mixture into pie pastry.
Bake for 40 to 45 minutes, or until knife inserted in the center comes out clean. Remove pie from the oven and place on a cooling rack. Immediately sprinkle remaining ⅓ cup of toffee pieces over the top. Cool completely before serving.