General rule is 20% for auto, 15% for manual.
Aluminum flywheel, carbon fiber driveshafts, aluminum wheels also make a significant difference.
Especially everything that is BEFORE any gear reduction. Such as flywheel weight.
In a 4.11 car, a 1 lb lighter driveshaft is equal to taking 2 pounds off of each rear wheel. And depending on your transmission, lightweight pistons and a light rotating assembly can be worth more than 10 times their weight in rear wheel torque.