Mix soy sauce, calamansi or lemon juice, banana ketchup, dark brown sugar, garlic powder, ground black pepper, and salt in a bowl. Stir until blended.
Add sliced pork shoulder to the bowl; marinate for at least an hour.
Prepare your pressure cooker, add marinated pork and sauce, lock the lid, set to high pressure.
Cook under high pressure for 20 minutes, then perform a quick release.
Open the lid, thread the pork onto skewers.
Preheat grill to medium-high, grill skewers for 10-15 minutes, turn occasionally.
Brush skewers with lemon or lime soda during the last few minutes of grilling.