I replaced the injector tips on my 05. The engine was starting to sound a little rough. After doing some research, I sent the injectors to F1 diesel, and had them test and install their nozzles. The cost was $1400. The engine runs smoother, but no change in performance. The only problem was that it took 3 weeks to get them back. The job itself is not too bad, but the forums are full of people who run into problems.