Q2 Diff - £500 all in at AutoLusso. Insurance wouldn't know as it is inside the gearbox.
Remap £250 at Red Dot, £200 if you join the AlfaOwner club (£25). Insurance could check this, but the chances are low. Alternatively, you could buy the Steinbauer P-box (not sure of price) at AutoLusso, which you could always remove in the event you needed to claim on the insurance.
If you DO want to declare it to the insurance, then you are one of a very small group of people!
