Cook pasta according to package directions; drain and return to pan. Toss with 2 tablespoons of the olive oil. Keep warm.
Meanwhile, in skillet heat the remaining 2 tablespoons olive oil over medium-high heat. Stir in peppers, onions, and garlic; stir-fry 4 to 6 minutes or until crisp-tender. Add shrimp and cayenne pepper. Cook 2 to 3 minutes more or until shrimp are opaque, stirring occasionally. Serve over pasta. Serves 4.