Preuninger said "385" was conservative and intimated higher actual output.
Stage 1: popping in the fuel map from the 991 Carrera S (400).
Stage 2: popping in the X51 from the 991 Carrera S (430).
I suspect Porsche have given themselves headroom for the mid-life 15-25 BHP lift on the "base" GT4, whist also allowing a further 20-25 BHP for the GT4 RS.
The point is, the Carrera S 3.8 unit can already do this as it stands, for the GT4 life-cycle "roadmap" described above.