In a small bowl, whisk together the brown sugar, paprika, garlic powder, cumin, chili powder, salt, and pepper. Cut the pork into 6-8 smaller pieces, and rub the spice mixture over all surfaces of the meat.
To make the sauce, whisk together the barbecue sauce, beef broth, and apple cider vinegar in a small bowl or measuring cup.
Heat 2 tablespoons of oil in the Instant Pot using the sauté function. Add the pieces of pork to the pot in batches, and cook 2-3 minutes per side, until lightly browned. Repeat with the remaining pieces of pork.
When all of the pieces have been browned, return the pork to the pot, and pour the sauce over the top. Place the lid on the pot, turn the knob to seal, and cook at high pressure on the manual setting for 30 minutes.
Let the pork manually release for 10-15 minutes, then turn the knob to quick release. Open the lid carefully to prevent burns.
Shred the pork pieces, discarding any chunks of fat, and place on a rimmed baking sheet. Drizzle 1 cup of the sauce over the top of the pork. Broil 5-10 minutes, or until the pork is just slightly crispy and browned. Serve hot.