Someone mentioned their engine was knocking bad. That usually happens when you have an injector nozzle stuck open. You can find the bad nozzle by loosening each injection line nut one at a time until you find the bad one. Loosen the nut 1 to 1 1/2 turns and if the knock stops then the nozzle is stuck open or defective. If it doesn't stop then continue checking until you find the bad one. If knocking stops when the injection line is loosened then raise the engine speed to about 2000 RPM and listen for the knock. If the knock does not resume then remove the nozzle and have it tested. It might could be repaired instead of replacing it.

The above is the way I did it on my Mercedes diesel and the process is the same for any diesel. I was able to disassemble my Bosch injectors and clean them, but I have never taken a 6.2 or 6.5 apart. If I ever get a bad one then I will probably disassemble it to see if a piece of carbon or metal is stuck in the nozzle. You don't have to be in a clean room, but you must have a very clean area, fuel or solvent, and pans.