They are easy to take apart. I used carburettor cleaner and rags to clean the carbon off the nozzles. The Carb. cleaner doesn't dissolve the carbon (no pun intended) but you may know of some other chemical that works. Just be sure to not use any abrasive materials. Always keep one injector un- dismantled so you have a reference to how the washers go back together... one has a groove and goes up a certain way. Diesel mechanics will probably shudder to think we are doing this, but my truck ran better afterward and there was a surprising amount of very fine material in the base of the injector holder when pulled apart. You'll need the copper washers that seal between the head at the bottom of the injectors and new aluminium washers for under the return lines. I didn't take out the copper washers part way up the bore, they were too compressed into the alloy head to risk it. However, I do think that new injectors and a proper set up are required periodically.