Combine the olive oil, 3 tablespoons soy sauce, and hot chili oil in a small bowl.
Combine garlic powder and pepper in another small bowl.
Place beef in a large, shallow dish. Pour half of the soy sauce mixture over one side of the steak and sprinkle it with half of the garlic mixture and half of the chopped cilantro. Rub mixture into the beef. Turn the steak over and repeat. Cover and refrigerate for 20 minutes.
To grill: Grill uncovered over medium heat, 17-21 minutes, turning occasionally. While grilling, combine the lime juice, brown sugar, and the rest of the soy sauce and pepper in a small bowl and near the grill grid to heat. To broil: Place beef on rack in broiler pan 3-4 inches from heat. Broil 16-21 minutes, turning once.
Carve steak into thin slices and arrange. Spoon sauce over beef. If desired, garnish with lime slices and cilantro sprigs.