After the initial problem of engine stalling, white smoke coming out, engine smelling gas - I replaced a fuel pressure regulator (brand new bought from dealer) plus ended up replacing 6 fuel injectors. The car ran well for about a few days and then the problem came back. This time our diagnosis pointed to four injectors going bad. We replaced those four and then the car was fine for a few days until the problem recurred again. However, when the supplier received the four injectors had those injectors tested they said there was nothing wrong with the injectors. But they shipped us the four replacements anyway. This leads me to question if there is anything else that could be causing the problem.