yes this is the SST to test the 2nd stage pressure - it should pop at about 5000 psi or so. - When disassembling the nozzles dont use bare skin on the injection tip and use a torque ratchet/wrench to tighten the injector halves to approximately 22 lb/ft (If I remember right) - this torque can change the pressure and may cause nozzle siezing too if attention is not given to these critical steps. Test and adjust the break pressure and carefully check the spray pattern too.
once you set the 2ndry pressure you can disassemble the nozzle, remove the SST and test the primary pressure - which is 2500 psi.
So make sure your diesel technician cheetah ustaad with mostache has a nozzle tester that has a 0-8000 psi scale at least and owns this Toyota/Denso SST.
If the shop doenst have these - move on and find one which has. - If none have these - then buy your own tester, shim pack and SST and figure out a way to do it yourself.