Shut down like turning the switch off. High pressure pump was not building enough fuel pressure. Not liking how this playing out. New pump and fuel regulator increased pressure, just not enough. Looking for a injector stuck open, not allowing pressure to build.
If you haven't already started doing your own research to figure out the problem, start now!
Some of these shops are more parts changers than mechanics. They start changing expensive parts and when that doesn't fix it, they move onto something else. Reality might be, they haven't got a freakin' clue.
Keep us posted ....