Now with correctly set adjustable ARBs and properly restrained ponies - there is no need for a Quaife.
Oh, final comment to report - I too now hear the 'whine' from my DSG in 2nd gear - I think this was also reported by RedRobin.
....I agree with your findings about the big benefits of these engine mounts but am surprised by your Quaife comment. I can see how the mounts would lessen the work the Quaife needs to do but I need convincing that a Quaife is of no benefit when such engine mounts are installed. Or am I taking your words too literally?
A Quaife, or any ATB diff, works by apportioning torque to the side which has the most grip.
On a 'normal car' (ie unmodified), loss of traction from one side is simply down to differences between the co-efficient of friction between the tyres (and therefore, the tyre with the lower friction, or grip, will spin and brake traction - with an open diff). The obvious cause is lack of wheel control from the suspension - correctly set ARBs will reduce this quite dramatically. But another cause of loss of traction is abrubt variations in radial/axial torque control - two fundamental causes - 1/ excessive play in the mounting of the powertrain assembly (the engine & tranny 'rocking' backwards and forwards around the same axis), and 2/ intermittant interuption of torque delivery by traction control systems (either by momentarilly killing the ignition, or by momentarilly braking driven wheels). By eliminating powertrain play, the transmission of torque is vastly more consistent (no more axle tramping or wheel hop).
So, with uprated engine mounts, AND correctly set ARBs, and turning off the ESP - the need for a Quaife or similar is VASTLY reduced. I have to try VERY hard - seriously hard, to get any cross axle loss of traction. But then I do run decent boots!
Obviously it's reassuring and good to know you're hearing the same (or similar) 'whine' as on my car. There's absolutely no effect on performance that I can detect due to the 'whine'. Fortunately I'm someone like Mat who actually enjoys all the added sounds from the engine bay - As one becomes familiar it becomes easy to spot any changes in sounds which may herald a problem which needs solving. I absolutely hate quiet cars!
Usually, whining from gearboxes is NOT good - however, this seems to be a 'factory fitted' trait!