Yes, FPR means fuel pressure regulator. If your car is starting up when you pinch the return line, something isn't right with the FPR. It should be doing the pinching, not you. You may have gotten a brand new faulty FPR. Stranger things have happened :-p I'm not sure if there's a way to test the FPR outside of making sure that it holds vacuum. You gotta realize that its up against about 60 psi of pressure and the smallest imperfection in the valve inside of it may cause it to leak. You could pull the little return line off of the FPR and then jump the fuel pump relay terminals to operate the pump to bring the system pressure up. Watch for fuel to come through the FPR. It shouldn't be siphoning fuel through when the engine is off. Be sure to use a rag to catch any fuel that comes out. Wouldn't want to spray the engine with gasoline.