Combine all spices to make the fuego spice mix. Can be stored up to 6 months in an airtight container
Squeeze the two oranges into non-reactive container. Combine with remaining ingredients for the agua negra marinade, including the orange peels. Stir with a whisk. Can be stored in the refrigerator for 2 days.
Trim away excess fat from pork and cut into 3 inch cubes.
Cover meat with 1 cup of fuego spice mix. Press into meat to help it stick.
Add seasoned meat to marinade, cover tightly, and refrigerate overnight.
When you are ready to cook, heat oil or shortening in a large heavy skillet over high heat until fat is smoking; add pork and brown completely on all sides- about 15 minutes.
Add reserved marinade plus 1 cup of Pepsi, and simmer for about 2 hours or until pork is tender and dark brown. Add additional Pepsi as needed while cooking to keep meat covered.
Remove meat and pull pork into strips. It should almost fall apart.
Optional: Place meat onto baking sheet and place in oven under broiler for 3-5 minutes to crisp up edges.
Serve with cheese, tortillas (flour or corn), lettuce, tomatoes, salsa, sour cream, and any other fixings you like.