Its 97% borrocks.
The 3% that isn't borrocks is that the ABS, ASR and VDC are tuned slightly differently if a Q2 is fitted as standard.
It seems reasonable that they might work very slightly better as a result.
The Q2 still works fine as a retrofit, and far far far better than the car as standard!
In reality the only thing that you may notice is that when you are at fuill throttle the ASR will sometimes behgave more abruptly on a car that had it retro-fitted.
The Q2 diff has minimal impact on the ABS as far as I could feel, I couldn't notice any difference in braking over a car that didn't have the Q2 fitted as standard.
In fact Torsen maintain the Mechanical Q2 diff (Torsen T2) is fully compatible with any ABS system.
However I do reckon it is theoretically possible that braking into a corner with a car that was equipped with Q2 from the factory could have very marginally better balance..
The reason being, that the Q2 diff, like many LSDs, works slightly under braking as well, so a truely optimized ABS system might be able to take account of that and bias the brake effort slightly differently accross left and right wheels.
I would guess that the VDC/ASR tuning would be about allowing the driver more aggressive use of the throttle before starting to brake wheels or cut fuel.
IMHO Its no big deal though - these systems are setup to have a wide operating range. Once you change to stickier tyres and to upgraded pads - much of the originals car balance will have changed.
Many people have retro-fitted the Q2, all have raved about it.
I've just been informed that Alfa do not recommend fitting the Q2 to non Q2 cars as the Q2 unit interacts with the VDC and ABS and that this would not happen with a Q2 diff fitted to an older alfa.
What are the effects of this? As anybody noticed any advirse effects of fitting Q2?