Have a listen at the
F80 M3 with its bi-turbo s55 inline 6 cylinder engine and exhaust during a cold start.
This M3 sounds a bit 'off', particularly during idle, so perhaps the exhaust is still being tuned on this car or the recording device has distorted the actual sound. The M3/M4 has sounded better in previous videos (reposted below).
Previous low speed videos: