Pierce sweet potatoes with a fork; rub with 2 teaspoons oil. Wrap each potato in foil. Bake at 400 degrees F for 1 hour or until tender. Reserve 5 roasted potatoes for Sweet Potato Cakes with Chicken and Poblano Relish and Sweet Potato-and-Mushroom Risotto.
Heat remaining 1 tablespoon oil in a large ovenproof skillet over high. Sprinkle pork with 1/4 teaspoon pepper and 1/4 teaspoon salt. Add pork to pan; cook 6 to 8 minutes, turning to brown on all sides. Place pan in oven; bake at 400 degrees F for 18 minutes or until a thermometer inserted in center registers 145 degrees F. Let stand 10 minutes. Cut pork into bite-size pieces.
Bring remaining 3/4 teaspoon pepper, remaining 1/2 teaspoon salt, ketchup, and next 4 ingredients (through garlic powder) to a simmer in a small saucepan over medium; cook 10 minutes or until thickened, stirring occasionally. Add pork; toss to coat.
Unwrap remaining 4 potatoes. Partially split potatoes in half lengthwise. Top potatoes evenly with pork mixture, sour cream, and onions.