injector replacement

After I messed around with my. Pre cups several times I apparently screwed up an injector. I was smoking worse than my deutz so I cracked fuel lines and isolated the 4th cyl.so I ordered 1 from Regal.
My question is:
Is It bad practice to replace only one or is it recommended to do all. The of course I have little history but d4 7u claims to have 3800 hrs. If it matters

Thanks for letting me tap the collective knowledge

I was tought to replace all four and have always done so. If one nozzle is stronger than the other three then one cylinder will operate differently than the others. You might get by replacing the damaged nozzle with a used nozzle but you'd have to test the three old nozzles and the used replacement nozzle to insure they were comperable. CAT sells nozzles for $50 each. I was tought not to buy aftermarket and after a demonstration on a test pump I learned why. Waste the $200 and buy CAT if you are not able or do not want to try a used replacement. Make sure to coat the injector with antisieze before install. I am partial to the copper variety CAT sells; it works well in the nastiest places.

I'll keep that in mind once I get the radiator in and make sure everything is good on the machine. For now, just for testing the aftermarket will have to do.

Thanks