In A Large Resealable Plastic Bag, Combine The Flour, Garlic Powder, Salt And Pepper. Add Rib Pieces; Shake To Coat. In A Pressure Cooker, Brown Meat On All Sides In Oil; Drain. Combine The Water, Ketchup, Chili Powder And Hot Pepper Sauce; Pour Over Ribs. Add Onion. Close Cover Securely; Place Pressure Regulator On Vent Pipe. Bring Cooker To Full Pressure Over High Heat. Reduce Heat To Medium-High And Cook For 15 Minutes. (Pressure Regulator Should Maintain A Slow Steady Rocking Motion; Adjust Heat If Needed.) Remove From The Heat; Allow Pressure To Drop On Its Own. Skim Fat From Sauce If Necessary And Serve With Ribs If Desired.