First, (if you haven't already) mix together all of the ingredients for the spice rub in a bowl using a fork to get rid of any lumps! You only need 1/4 cup of this rub, so you can save the rest for later.
Next, rub the spice mixture all over your pork roast with your hands. Be sure that every inch of the roast is covered. Set aside.
Turn on the Instant Pot's saute feature and add two tablespoons of olive oil.
When olive oil is fragrant add pork roast and sear for 2-3 minutes on each side to brown the pork.
Remove pork from Instant Pot and deglaze your Instant Pot by pouring half of the broth (1/2 cup) onto the bottom of the pot. Scrape all of the brown bits from the bottom the Instant Pot with a spatula.
Next, add onion and garlic to the pot and cook for 2-3 minutes.
Then, add the rest of the broth to the Instant Pot and place the pork roast back into the Instant Pot.
Turn off the saute feature and then put the lid on. Seal the Instant Pot and set it to manual high pressure for 90 minutes. It should take a little bit to build pressure before it starts to count down from 90.
Once the timer goes off, quick release the pressure from the Instant Pot and remove the pork roast. Save 1 cup of the cooking liquid for later. Discard the rest of the liquid.
Place the pork back into the Instant Pot and shred it with two forks The pork should shred very easily. If it doesn't, you likely need to continue cooking.
Once shredded, Pour the remaining cup of cooking liquid and the bbq sauce over the pork and mix well.
Turn the saute feature on the Instant Pot and let the pork cook for 2-3 minutes. Serve immediately on your favorite bun!