1. For spice rub, if using chile in adobo, finely chop with sauce. Combine jalapneo flakes or canned chile and sauce with paprika, brown sugar, salt, cumin, red pepper, and garlic powder in a bowl. Rub spices on both sides of ribs. Transfer ribs to a jelly-roll pan and cover with plastic wrap. Marinate in the refrigerator 2 to 24 hours.
2. Heat oven to 300 degrees F. Wrap ribs tightly in foil. Transfer to a clean jelly-roll pan. Bake 1 hour. Transfer drippings to a bowl; skim off fat.
3. Heat and oil grill. Remove ribs from foil. Grill 10 minutes, turning ribs every 2 to 3 minutes and brushing each side with some of the reserved drippings.
4. Meanwhile, heat oil in a small saucepan over medium heat 1 minute. Add barbecue sauce and thyme sprigs; cook 2 to 3 minutes. Remove thyme, serve with ribs. Makes 4 to 6 servings.