No its becuase they kept using a 270 degree thrust bearing system in the turbo instead of the 360 it needs to support the thrust loads.
With the 270 degree system there isnt enough oil in between the thrust bearing to support such a big compressor wheels thrust, and pretty much just pushes out the oil out of the way. Especially when closing the throttle after high boost. If you can hear your blow off valve flutter after you relased the throttle under high boost, it is removing and applying thust load on that thrust bearing mulitple times, and killing it.
http://www.turbomagazine.com/tech/04...t_1/index.html
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