I have never needed to replace a fuel injector in anything--I have upgraded them to higher capacity numerous times. Cleaning them is easy, I connect a 4" or so long piece of vinyl tubing; of appropriate ID to fit snugly; to the outlet end of the injector,. Next fill the tube with cheap Super Tech carburettor cleaner from Walmart. Pressurize the tubing with compressed air to 40 to 45 psi¹ then activate the injector. Do that 2 or 3 times and it will be clean. Some do this from the inlet end, however I have found back flow flushing to be more effective.
I also have a rig using a 100 cc graduated column (actually a big syringe) that allows me to time how long it takes the injector to squirt 100 cc of fluid--I use naphtha--that provides a pretty good indication of it's flow rate.
CAUTION: Make sure you do any of this in a well ventilated area--and use an enclosed switch to trigger the injector. Flammable aerosols and nearby sparks can make bad things happen!
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¹ - Most fuel injectors are rated at an operating pressure of 3 bar (43.5 psi).