Tens of pounds + saved.
For example, the stock 20 inch rims that comes standard with the P3D+ weight 28.75 lbs. The stock 18 inch rims weigh 21.6 lbs (Without Aero Cover), 23 lbs (With Aero Cover) .
Getting monoblock forged rims in 18 inch would weigh 17.4 each, giving you 4.2 lbs saved per...