"Dropping in forged pistons" is not a simple task. The manufacturer will have extreme difficulty passing cold start emissions and suffer from reduced motor lifetime. Alternatively, it is actually possible to forge hypereutectic (high si doped Al) material. This is likely what would need to be done. Keep in mind the silicon doping process increases the fragility of the material.
AWD BRZ STi 2.5-liter turbo reported to be in the works
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