Right, if he had an injector leak the thing would have pig rich running issues. And other than I've NEVER had a fuel pumps pressure relief valve do that to a car it is a possibility. BUT with that said you still have to perform tests to determine whether it would be the regulator or relief valve. Since the regulator first the easier one to test, test that first by replacing with a known good unit, if your problem is solved, cheers. If not, move onto the pump