How to Make It
Preheat water with immersion circulator in large stockpot to 145°F according to manufacturer’s instructions.
Stir together ketchup, vinegar, mustard, brown sugar, Worcestershire sauce, onion powder, garlic powder, oregano, paprika, chili powder, cayenne pepper, 1 teaspoon of the salt, and 1/2 teaspoon of the black pepper in a small bowl. Set aside.
Fold over tops of 2 vacuum sealer bags about 1 1/2 inches to keep tops of bags clean. Carefully place 4 pieces of meat in each bag, and pour 1/2 cup sauce in each bag. Cover and chill remaining sauce until ready to grill meat. Massage each bag to ensure meat is coated in sauce, and spread meat pieces in an even layer in each bag. Using a vacuum sealer, remove air and seal bags tightly according to manufacturer’s instructions.
Place bags in preheated water, and cover top of stockpot with aluminum foil to reduce evaporation. Cook until meat is done, 18 to 20 hours.
Remove bags from water, and let stand 10 minutes. Transfer bags to a bowl of ice and water, and let stand 10 minutes. Remove meat from bags, and place on a wire rack in a rimmed baking sheet. (If not grilling immediately, remove meat from ice bath, and cover and chill up to 1 week.) Pat meat dry with a paper towel. Rub meat with oil, and sprinkle meat evenly with remaining 1 1/2 teaspoons salt and 1 teaspoon black pepper.
Preheat a grill or grill pan to medium-high (400°F to 450°F). Grill meat, uncovered, until grill marks appear, basting occasionally with remaining sauce, 4 to 5 minutes per side. Slice meat, and serve immediately.