Just near in mind that the rear wheels are driven so that is part of the rotating mass.* The front wheels (assuming your are RWD) would be more likened to unsprung weight although both apply to all 4 wheels.
Rotating mass (and the intertidal it takes to accelerate it) is most applicable to flywheels, drive shafts, bob weight/crank mass but also ( though somewhat less so) * the wheels and tires. Also all driven loads (behind the motor) are effected by gear reductions and driveline slippage.
I'm very anxious to find out how much it helps. Of course, the rest is on a diet as well.
I did see that my little 287 (4.7) Dakota drops 3.5 tenths from bypassing the alternator, power steering and AC idler pulley.
