Add the pork or chicken, garlic, and chili and stir-fry for 1 minute. Stir in the drained noodles and the reserved fish sauce mixture and stir-fry about 30 seconds. Add the shrimp and stir-fry just until they turn pink. Remove from the heat and transfer to a serving plate. Garnish with the remaining bean sprouts, cilantro sprigs, and lemon or lime wedges, and serve immediately.
Diners squeeze lemon or lime juice to taste.