In a large flat container or bowl, mix the oregano, chili powder, cumin, salt and pepper. Sprinkle all sides of the meat with the mixture and place in the instant pot.
5 lbs. pork shoulder, 2 tsp Mexican oregano, 1 tbsp chili powder, 2 tsp ground cumin, 2 tsp salt, 1 tsp pepper
Place the onion and chilis in the instant pot. Then place the garlic, cut side down, on the meat.
1 onion, 1 head of garlic, 3 serrano peppers
Pour the orange juice, lime juice, and coke over the meat.
2 oranges, 2 limes, 1½ cups Coca Cola
Seal the instant pot and set the meat cycle for 90 minutes.
When the time has finished, let it slow release.
Open and place the meat on a cutting board or plate. Remove any pieces of fat and using two forks pull the meat apart.
Set the broiler for 500°F and cover a cookie sheet in tin foil.
Place meat on the cookie sheet. Spoon some of the broth over the meat. Place under the broiler till crispy, about 5 minutes. Stir the meat and crisp again.
Remove meat from the oven and serve.