[BMW269]

The M3 GT4 doesn't really have less power or torque than the M3 GTS, as it has Full Akrapovic Evolution System. But the M3 GTS specs might be conservative, and I would say it has closer to 460 PS, 440 Nm is correct, it is the displacement.
4.0l V8: 105 PS/l -> 420 PS, 100 Nm/l -> 400 Nm
4.4l V8: 105 PS/l -> 462 PS, 100 Nm/l -> 440 Nm

I do not remember who's M3 E92 it is, but it is AW with 18 "OZ Superleggera rims. It has Akrapovic full exhaust, Brembo brakes or maybe just uprgraded stock brakes, ECU tune and KW V3 CS, but is not stripped out, it has navi and so, and it ran Hockenheim slightly faster than M3 CSL, and the N-Ring also in 7:50 min. So for the M3 GTS 7:40 min is sure, if not better. But we'll see. As the the M3 ZCP I think the 8:00 min N-Ring is with is with stock tires.
8:13 min: M3 6MT with 18" rims and stock tires
8:05 min: M3 6MT with 18" rims and sport tires
8:00 min: M3 ZCP 7DCT with 19" rims and I think stock tires