Combine orange juice, onion, chipotle chili powder, cumin, salt, and garlic in your Instant Pot. Add pork, tossing to coat.
Close and lock the lid of the Instant Pot. Turn the steam release handle to Sealing position. Press Manual; select High Pressure, and use [-] or [+] to choose 29 minutes pressure cooking time. When time is up, turn cooker off. Open the cooker using Natural Pressure Release.
Remove pork from cooker with a slotted spoon; shred with 2 forks to measure 4 3/4 cups meat. Remove and discard any chunks of fat.
Spread pork in a single layer on a jelly-roll pan or broiler pan lined with foil.
Skim fat from cooking liquid in cooker; discard fat. With lid off, press Sauté, and use Adjust to select “More” mode. When cooking liquid comes to a boil, turn cooker off.
Press Sauté, and use Adjust to select “Normal” mode. Simmer, uncovered, 5 minutes or until slightly thick, stirring frequently.
Preheat broiler. Drizzle pork with 1/4 cup cooking liquid. Discard remaining cooking liquid, or set aside for serving, if desired. Broil pork 3 to 5 minutes or until pork is browned and edges are crispy, turning pork occasionally.
Heat tortillas in microwave according to package directions. Spoon 1/3 cup shredded pork mixture onto each tortilla. Top each with about 3 tablespoons tomato and about 1 1/2 teaspoons cilantro. Serve with lime wedges, if desired.