[jphughan]

I like the noises too, better than adding yet more weight with sound insulation or using quieter and likely less heavy duty equipment, or achieving quiet without those tradeoffs by driving up the cost. The M3 supplement manual says that these noises are normal. That lift-off noise you're hearing is probably the tranny or diff because of the sudden load change. It's most evident when in 2nd gear, accelerating full throttle to redline, and then abruptly lifting off the throttle. Nothing to worry about.