Preheat oven to 350°F. Line four 4 x 2-inch mini loaf pans with aluminum foil extending foil 1 inch above top of each pan. To prepare Streusel: In small bowl with fork, stir together 1 cup of the flour, the brown sugar, pecans, cinnamon, and nutmeg; stir in 1/2 cup of the mayonnaise until well mixed. In medium bowl stir together remaining 1 1/2 cups flour, the granulated sugar, baking powder, baking soda and salt. Make an indentation in center; add remaining 3/4 cup mayonnaise, the eggs and vanilla; stir just until dry ingredients are incorporated (mixture should not be smooth). Divide half the batter among loaf pans; spread to make even layers. Evenly crumble 1/4 cup of pecan mixture into each pan. Add remaining batter; spread to make even layers. Crumble remianing Streusel on top; lightly pat into batter. Bake until a toothpick inserted comes out clean, 35 to 40 minutes. Cool 5 minutes in pans before removing.