In a large bowl, whisk together sour cream, 1/4 cup sugar, eggs, 1/4 cup flour and vanilla extract. Fold in apples and toss. Pour into pie shell. Mix together oats, 3/4 cup all-purpose flour, 1/4 cup sugar, and ground cinnamon. Either in the microwave or on the stove melt the peanut butter and butter together until smooth. Add to the oat mixture and sprinkle over apples. Bake in preheated 350 degree oven 50-55 minutes until golden brown and center is set.