Others are pointing toward lack of fuel pressure in the rail, and that sounds like a good reason swapping parts hasn't solved it. Have your son try this:

With the ignition key in his pocket, fashion a jumper wire between fuse terminals 4 and 6 like this:



Then ask him to listen for the pumps (both) under the rear seat and in the tank.

Then while the pumps are on, pull the hose from the front of the fuel pressure regulator. You don't want him to see any fuel coming out here:



If all is well, so far, there should be fuel surging through the return line exiting from the rear of the fuel pressure regulator. If so, you can get as close to actually verifying with a pressure gauge, that fuel in the rail exists at the pressure necessary for fuel injection to occur.




--
Art Benstein near Baltimore

I want to die peacefully in my sleep, like my grandfather.. Not screaming and yelling like the passengers in his car.