To Make Cheesecake Layer: In a medium mixing bowl, beat cream cheese until smooth. Beat in 1/4 cup sugar, then add vanilla extract and 1 egg. Beat mixture until light and smooth. Chill mixture for 30 minutes, then spread into pastry shell.
To Make Pumpkin Layer: In a large bowl, combine pumpkin puree, evaporated milk, 2 eggs, 1/4 cup brown sugar, 1/4 cup white sugar, cinnamon, nutmeg, and salt. Mix until all ingredients are thoroughly combined.
Pour pumpkin mixture over cream cheese layer. Cover edges of crust with aluminum foil.
Bake in preheated oven for 25 minutes. Remove foil from edges and bake an additional 25 minutes.
To Make Pecan Streusel Layer: While pie is in oven, combine flour and 2 tablespoons brown sugar in a small bowl. Mix well, then add softened butter or margarine and stir until ingredients are combined. Mix in pecans.
After pie has been in oven for 50 minutes, remove and sprinkle pecan streusel evenly over top. Bake for an additional 10 to 15 minutes, until a toothpick inserted in center comes out clean.