Cook pasta according to package directions, omitting salt and fat. Drain, reserving 1/4 cup cooking liquid; keep warm.
Remove green tops from green onions; thinly slice, and set aside. Mince white portions of green onions; set aside.
Heat oil in a large nonstick skillet over medium-high heat. Add minced green onions, bell pepper, pork, and mushrooms; sauté 3 minutes or until pork is browned. Combine reserved 1/4 cup cooking liquid, teriyaki sauce, and chili garlic sauce in a small bowl, stirring with a whisk. Add pasta and teriyaki sauce mixture to pan; toss well to coat. Stir in sliced green onion tops.