For what it's worth, the Simjet Nexus used the same cast compressor as the Wren 160. It also had issues blowing up compressors with about 5-6 hours on them. many people have had good luck installing the CNC Wren 160 wheel on their turbines. The interesting part is the Nexus had a max rpm of around 117-118k. Once the CNC compressor was installed, many people increased their rpm to around 121k.

One thing I noticed on my Nexus is that once the compressor was spaced far enough forward to have the proper clearance with the inlet, it left a significant step between the compressor and the front face of the diffuser. This would cause a high pressure/low pressure scenario and some shear. The shear sounds like a high pitched whine and may result in a frequency that over time could cause the resonance stated earlier.

I think that removing the shims, and moving the compressor back to eliminate the step would be ideal. This would require machining the front of the diffuser and the radius around the outside to move the inlet lack to the compressor. This would achieve a smoother flow of compressed air with less shear.

Wren has always been great to deal with and more than fair with me. They also came to the rescue when my nexus was in need of a compressor.
Just my thought.....