How difficult is it to install new nozzles on your injector bodies? I've been thinking about it for a while, I'm closing in on 300k miles and it would probably be a good idea at this point.
It’s fairly simple to DIY but there are things you need to consider first.
1: They need to be poptested at 2 stages based on the RPM target for max flow. This is achieved by hydraulically popping them and recording the pressure then adjusting things via shims until all 4 are popping the same and then again at a higher pressure based on the target.
The professionals like Kerma, or Malone and so on all do this with a flow bench and a pulse to ensure its delivering correctly.
On light to stock nozzles you can get away with just assembly and drive them but there is still a small risk they may not be right. You can pop test them yourself simply with a bottle jack and some brake lines and fittings and such.
2: you need a clean environment. if you have a box fan and a merve 18 filter making a down draft setup is good enough with gloves and lint free rags... coffee filters are a good solution for rags as there lint free and cheap. Everything must be clean; you cannot see the dust that will damage things smaller than 30 microns.
3: to have kerma or anyone else do the job is cheap, usually $150 for all 4 with a hot swap option available. They send you the injectors assembled with your new nozzles ready to go and you send them your old cores and they refund the core charge.
Possible damage can be anywhere from bad economy to a melted piston in extreme cases. The tips of the nozzles must not be touched even when assembled.
Spend the few bucks and have them done via hot swap. I do like kerma, others have had issues with them but there are other options I encourage you to research and talk to tuners.