Preheat an 8-quart air fryer to 390°F for 3 minutes. Pat chops dry and rub with oil, salt and pepper.
Simmer mustard, ketchup, brown sugar, vinegar, water and garlic powder in a small saucepan for 3 minutes, stirring. Reserve half in a clean serving bowl.
Arrange chops in the basket in one layer with space between them. Air fry for 7 minutes, turn and cook for 4 minutes.
Brush with the cooking portion of sauce and air fry for 2 to 5 minutes more until the thickest meat reaches at least 145°F. Discard remaining cooking sauce and brush residue.
Rest for at least 3 minutes and spoon the reserved clean mustard-barbecue sauce lightly over the chops to serve.