In a large bowl combine egg, water chestnuts, bread crumbs, ginger, garlic salt, and black pepper. Add ground pork; mix well. Shape pork mixture into eighteen 1-1/4- to 1-1/2-inch meatballs.
On six long metal skewers, alternately thread meatballs, sweet pepper pieces, and onion wedges, leaving 1/4 inch between pieces.
For a charcoal grill, arrange medium-hot coals around a drip pan. Test for medium heat above the pan. Place skewers on a well-greased grill rack over pan. Cover and grill for 12 to 15 minutes or until meatballs are no longer pink and juices run clear (160 degrees F), turning and brushing with Five-Spice Hoisin Sauce occasionally. (For a gas grill, preheat grill. Reduce heat to medium. Adjust for indirect cooking. Grill as above.) Serve skewers with plum sauce.
Five-Spice Hoisin Sauce
In a small bowl stir together hoisin sauce, orange juice, five-spice powder, and dash crushed red pepper.