If you're making it in a stove top pressure cooker or in a 8 quart or larger electric pressure cooker, you will likely need to increase the water.
1 to 2 tablespoons/15-30ml vegetable oil
4 pounds/2kg boneless pork shoulder, cut into two equal pieces
2 cups/500ml barbecue sauce, divided, plus more for serving
1/2 cup/125ml water
Toasted rolls, for serving
Select Saute to preheat the pressure cooking pot. When hot, add the oil to the cooking pot. Brown pork on both sides, about 3 minutes per side. Brown each half of the roast separately. Remove to a platter. Add 1 cup/250ml barbecue sauce and the water to the cooking pot. Stir to combine. Add browned pork and any accumulated juices to the pot.
Lock lid in place. Select High Pressure and set the cook time for 75 minutes. Allow the pressure to release naturally (approximately 20 minutes). Carefully remove the lid. Remove the meat from the pressure cooker and shred with two forks, discard excess fat.
Strain cooking liquid, reserving 1/2 cup/125ml. (Optional: Use a fat separator to separate fat from the juices.) Place shredded pork in the cooking pot with remaining 1 cup/250ml barbecue sauce and reserved 1/2 cup125ml cooking liquid. Stir to combine and bring to a simmer, stirring frequently.
Serve on toasted rolls with additional barbecue sauce, if desired.