The chattering sound comes directly from the transmission as harmonic vibrations are not "muted" by the springs of the FW, as there are no springs at single mass flywheels.
@cstavaru: I hope that misfires will go away with this setup. Spark plugs didn't help at all, not even swapping coils. So, it must be the flywheel. If it doesn't help, I'll search for a DME malfunction or try to suspend misfire detection if possible from my tune.
I forgot to say that it was not the first time I worked with Jeff for getting parts for my car or for my friend's car. It must be the 3rd clutch kit I bought from topgearsolutions along with other stuff such as ER break lines etc.
For future search here is a link regarding
BMW 335i Spec Stage 2+ Clutch Kit from the vendor's website. Jeff offers great international posting fees if anyone is interested, just ask for a quatation