Thinly slice the sausage and set aside.
In a 3-quart skillet, heat the oil over medium heat. When the oil begins to smoke, add the sausage, onion and garlic and cook until slightly browned, 4 to 6 minutes. Add the tomatoes and asparagus and cook until the asparagus is tender, 6 to 8 minutes. Add the chopped parsley and season with salt and pepper.
Meanwhile, place a large grill pan on 2 burners over medium-high heat, or preheat an outdoor gas or charcoal grill. Lightly oil the pan or grill grates. Sprinkle each chicken breast with the onion and garlic powder and salt and pepper to taste. Grill the chicken until cooked through, 4 to 5 minutes per side. Transfer to a plate and keep warm.
Cook the pasta in a large pot of boiling, salted water until al dente, 9 to 10 minutes. Drain and add the pasta to the sauce; toss well and divide among 8 bowls. Slice the chicken breasts and divide them among the bowls. Garnish with additional parsley and serve immediately.