I always thought fatigue kills a piston, so knocking is the primary reason destroy piston/con rods, right?

Will knocking off a cat cause the afr go off by that much?

U can download "knock detection" for ur torque app, it reads the knocking correction value from ecu.

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MY08 STI 422whp at 1.5bar on E85, built by Diversion Garage, assembled and tuned by EvoR

Update from new owner: 375whp at 1.4bar on 98, at Tokyo Motorsport