In a small bowl, combine milk and vinegar. Set aside.
In a large bowl, combine flour, brown sugar, baking powder, pumpkin pie spice, salt, and baking soda. Blend well.
Using a grater, grate the cold butter into the flour mixture. Fold butter into flour mixture until well-blended.
In a medium bowl, combine the sour milk, egg, and pumpkin puree. Whisk until well-blended.
Add the pumpkin mixture to the flour, along with the pumpkin spice baking chips and pecans.
Mix altogether until just combined.
Turn onto a lightly floured surface, and knead 10-12 times. Gently form dough into a large ball.
Place the dough onto a well-greased baking sheet and flatten into a circle about 10-inches in diameter, and about ¾-inch thick.
For the streusel, combine all streusel ingredients in a small bowl, and mix until it resembles coarse crumbs.
Using one hand as a wall to keep the streusel onto the scone dough, sprinkle the streusel crumbs evenly over the scone dough. Keep as much of it off of the baking pan, and on top of the scones as possible. Press down lightly to press the streusel into the dough.
Using a long knife, cut into 8 wedges.
Carefully separate wedges on baking sheet, pulling them just slightly apart.
Bake at 400 degrees for 18-20 minutes, or until edges are golden brown.
Cool slightly, and serve!