if you are racing yes, if not what they said X2; a flywheel stocks energy only to be released when its mated with the transmission; a lighter flywheel means that you will need to increase rpm in order to release the same energy the stock flywheel was doing at a lower rpm because of its weight; a lighter flywheel will make you creep into the redline like a Ferrari engine, but Ferrari's are also 1500 lbs lighter than our 4200 lbs beasts; remember torque is what makes our babies move forward; you don't want to kill that if you are street performance only; there are many ways to shed 100lbs and thus gain a 10th on the quarter mile; that might not be the best way to go; imo