You may want to look at the last time he was tuned. There was a big hole in the coupler. For some ODD reason the tuner decided to finish the tuned even with the big ass boost leak.

Now if you keep that leak in mind and the fact that Ryu was still seeing 41 psi on the gauge. This makes it possible that the turbo was being severely over spun. It is possible that the turbo was in fact putting out over 50psi. So in reality the turbo blew bc of the tuners incompetence.