2012 S63 with with weistec race tune 700hp. Runs perfect except high rev, mostly manual driving, a loud vibration type noise occurs after throttle let off. The noise remains for several minutes of conservative driving, even coasting, and goes away after awhile, only returning again after spirited driving.
Thinking either belt/pulley issue somewhere or excessive turbo pressure creating surge, although surge doesnt usually last as long as this does. Or trans, or driveshaft, or...? Help!
I can slightly feel it under foot, very slight...thanks!