I was also told when I had my turbine serviced after a crash that the cast compressors expand over time due to centrifugal forces and part of the 25hr service is machining the compressor wheel to within tolerances again. Not sure if this is accurate as it's WAY out of my expertise, but I have NO reason to doubt them. My turbine is better than new now. They also re-glued several parts inside (oiler and such) that needed attention. Overall, a very good experience.