Easy to test the glowplugs with a multimeter at the glow-plug relay connector. While you have the injectors out, turn on the glow and peer down each hole to verify they are glowing red. Sometimes they can ohm OK, but have an internal short which puts the hot spot further up the body instead of at the tip (so I have heard).

The pop pressure may be over-rated. I found 3 of the 5 injectors in my 1984 popped at 1600 psig (non-turbo), and the others correct (~1950 psig). Yet, the engine ran fine and about the same when I put all correct ones in. The spray pattern can be hard to judge on a tester. On mine (long ram type pump, electronic pressure recording), some pumps can give more of a stream. You must pump fast enough to get it to "machine gun" pop. Someday I'll add an optical recording to better characterize the spray pattern and fineness than I can do by eye. I used to do academic research on sprays.