In a small bowl, combine all of the dry rub ingredients.
Throw pork butt pieces in a large bowl. Add the seasonings and mix well.
Stuff pork into 4 16-oz mason jars leaving about 1/2" head space. Close until finger tight. Alternatively, wrap the pork tightly in several layers of heavy duty aluminum foil.
Place the jars or the foil pack (seam facing up) on the removable rack of the Instant Pot. Pour enough water to reach about 1/3 of the height of the jars or the foil pack.
Cover the pressure cooker and make sure the pressure valve is sealed. Set for MANUAL, HIGH pressure for 60 minutes cook time.
When the pressure cook time is up, let the pressure cooker naturally release for 20 minutes. Then open the valve completely to quickly release all the remaining pressure.
Remove the jars or the foil pack from the Instant Pot. If cooking pork in mason jars, let the jars cool for about 20 minutes before opening them. If cooking in foil, let the pork rest for 5 minutes before opening.
Dump the meat in a bowl together with the liquids. Shred with forks, mix with juices and keep warm until ready to serve.
For smoky flavor, add about a 1/4 tsp of liquid smoke if desired. This stuff is potent so less is more in this case. If 1/4 tsp is not enough, add a few drops more.