There is no extra boost in LC Mode with the B58. I think the reason for the closer rolling race is very simple - just look at 3:08 in the video - the m240i pulls until he shifts, then he falls back - looks pretty much like a missed shifting point to me. After owning an M340i and having driven the Gold R as a loaner, I am pretty sure that the performance advantage of the m240i should be even bigger at higher speeds…I am very sure.
I think the figures shown in the thread I linked below confirm that too - the M240 is very close to the RS3.
G42 2022 M240i Dragy fun: 0-60 and 1/8 mile (vs RS3 and Supra times)
https://g42.bimmerpost.com/forums/sh....php?t=1885638
In other words: it might have been less close if you took Thomas out of the equation
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Car history:
1989 E32 735i, 1992 e34 535i, 2003 E39 540i, 2014 F36 430d, 2017 F22 M240i, 2018 F87 M2, 2019 G20 330d, 2020 M4 Competition, 2020 G20 M340i, 2021 M5 Competition