When grill is heated, place packets on gas grill over medium heat or on charcoal grill over medium coals; cover grill. Cook 15 to 20 minutes, rotating packets 1/2 turn after 10 minutes, until juice of chicken is clear when center of thickest part is cut (170ºF). Place packets on plates. Cut large X across top of each packet; fold back foil. Top with chow mein noodles.