Certainly not any harder than installing a transmission shift kit, at least as far as the teardown and reassembly goes. Of course if you have issues you would need injector test equipment to check for balance and nozzle break pressure, etc. But for basic cleaning, mods, replace broken spring, etc, certainly falls in the DIY category, IMO. In fact I've been informed (no names

) that not everyone building MOD'd injectors have the $15,000 test stands.
I initially got a few comments and messages from those who do rebuilds professionally suggesting it was a bad idea to encourage people to work on their own injectors. Not sure if it's trying to protect the monopoly of the few in the know or if it's actual concern for someone screwing things up. Funny as the tranny guys tend to be more helpful to people doing their own tranny rebuilds, but then thats an area where parts and info are easily obtained.
I'm reminded of the IDM mod that was a closely held secret of the few Joe Servo told about it. All the smoke and mirrors about needing a scope and special knowledge to do the Mod, when in reality that was only needed initially to develope the Mod, and after that just a matter of changing one resistor.
I'm not going to come right out and recommend you Mod your injectors, but it's certainly do-able and I won't discourage anyone with the will to take the risk from doing so themselves. I'll have one out of my truck tomorrow for an inspection teardown, so we'll see if I can make it work again. Have the replacement (torx) poppet screws and internal o-rings from Mylex International, so I'm anxious to get in there and do some damage
