The magnet is buried in the spinner nut...the aluminum inlet is nonmagnetic aluminum and has no effect. That would leave the sensor, the lead, or the processing circuitry as suspects. If you damaged the Wren enough to need a new compressorand inlet, my guess is that it was the sensor, since it is only millimeters away from the compressor......

Did you get a new tailcone along with the compressor to get that extra 2 lbs (or so) of thrust??