For the same engine power is the S58 potentially more efficient than the B58? It has a lower compression but the twin turbos and extra lag might help out a bit for the fuel tests?
My comment around lag is based on the fact that if the engine isn't coming on boost at all it can run leaner and hotter. Compared to perhaps a small turbo engine that comes onto boost super quick and needs to drop the AFR down to keep things cool and stop detonation?
In saying that I'm not trying to say that the Z4/Supra will ever get the S58