Liberally salt and pepper roast then brown on all sides 5-8 minutes using olive oil in the bottom of the pressure cooker pan.
While the meat is browning chop onions, green peppers, cilantro, and get garlic peeled/smashed.
Remove roast onto platter. Drain excess fat/oil from pan. Put grate in bottom of the pressure cooker (don't worry if you dont have a grate), add meat, onions, green peppers, garlic, cilantro and chipotles. Season all with cumin and oregano to taste, add 1 cup of water. ** If no Pressure cooker don't worry, cover meat with water and simmer for 1 1/2 - 2 hours till tender.**.
Close pressure cooker, bring to pressure, then reduce heat and cook at 15psi for 1 hour, let cooker cool down naturally.
Remove meat from cooker to rest for 5 minutes, discard veggies (or if you prefer extra SPICY shred them up with the meat). Reserve a small amount of the liquid in pan.
Shred meat with two forks (discard any fat/gristle), return to reserved liquid and keep warm on low heat until ready to use in burritos or tacos with your favorite fillings.