um, do you know how a FPR works?????? it has nothing to do with 'releasing' fuel to the injectors. all it does is exactly what its name says...fuel pressure regulator.

it doesnt release the fuel TO the injectos...it allows the flow of the fuel back to the tank. follow the fuel lines, from the tank, through the filter, to the rail, through the FPR, back to the tank.

put a noid light the injector clips to see if they are getting the right amount of fire inorder to open them up. you could also take a 12 volt supply to shock them to see if they are clogged.