You need to be checking the fuel pressure when it's NOT RUNNING, with the injectors and fuel metering valve (IMV) brown plug on the pump disconnected.

With the IMV disconnected the pump should deliver 1600bar pressure (f*ck knows what that is in psi!) Needs around 250bar to start/run.

If you have excess leak off the fuel pressure won't be 1600bar, more like 1000-1200bar if 1 or 2 injectors are fecked.

Another thing worth doing is disconnect the return to the filter briefly and drain some fuel into a cup or something, see if any metal particles floating around.