Mix pork, 2 tablespoons oil, soy sauce and 3 teaspoons cornstarch in medium bowl. Cover and refrigerate 1 to 3 hours. Mix 1 teaspoon cornstarch, broth and oyster sauce in small bowl.
Heat 1/3 cup oil in large skillet over high heat until very hot. Add half of pork; stir-fry 3 minutes. Transfer pork to strainer. Repeat stir-frying with remaining pork. Pour off all but 2 tablespoons oil from skillet. Add onions, poblano, bell pepper and garlic to skillet; stir-fry 2 minutes. Add pork, grapes, ground pepper and oyster sauce mixture. Stir until pork is coated with sauce. Serve immediately.
*Oyster sauce is available at Asian markets and some supermarkets.
**A fresh green chili, often called a pasilla, available at Latin American markets and some supermarkets.