Pour cola, orange juice and lime juice in a medium bowl. Add salt, pepper, cumin, chili powder, garlic powder, onion powder, paprika, oregano and crushed red pepper flakes. Whisk to combine and set aside.
Cut pork into 4 pieces (as evenly as possible). Pour oil into your instant pot and set to saute. When the oil is heated, add 2 pieces of the pork and sear until browned on all sides, using tongs to turn (approximately 1 minute each side). Transfer to a clean plate. Repeat with the remaining 2 pieces of pork.
Turn off the saute setting by pressing "cancel". Return the 2 pieces of pork on the plate to the instant pot, along with any juices.
Pour the juice and spice mixture over pork.
Place the lid on your pressure cooker and lock. Steam release knob should be on "sealing". Cook on manual setting (high pressure) for 45 minutes. Allow the pressure to release naturally for 15 minutes, then quick release the remaining pressure.
Carefully remove the pork from pressure cooker with tongs to a cutting board or large bowl. DO NOT DISCARD LIQUID in pressure cooker. Shred into small chunks using 2 forks. Remove and discard any fat pieces.
Spray a large rimmed baking sheet with cooking spray or line with aluminum foil. Transfer the shredded pork to prepared baking sheet and spread evenly.
Drizzle about ½ cup of the liquid from the instant pot as evenly as possible over the pork.
Broil under high heat in the oven for 5 to 8 minutes, or until the edges of the pork become crisp and begin browning.
Skim off any fat that has risen in the liquid in the Instant Pot and discard fat.
Before serving, drizzle desired amount of liquid over pork and toss to coat as evenly as possible.