[86TOYO2k17]

I have been researching this a lot as I have every other possible performance mod (besides FI) and was contemplating doing something like this. There are a lot of in depth articles discussing pulleys, flywheels, and driveshafts.
Long story short a fly wheel will increase performance about 4-6hp although you do lose inertial benefits in between shifts based on how quickly you can shift (be out of gear rpms drop quicker)

A driveshaft will add about a 1/8hp increase in performance from lessening rotational mass. Assuming a 15lb reduction and no increased diameter (like aluminum driveshafts have which make any gains from weight null)

Lightweight pulleys will have even less effect then driveshaft with most potential risk. Underdrive pulleys do work, how much depends on the percent the pulley is being underdriven. Typically you can gain .6hp from underdriving the alternator pulley, and 1hp from underdriving the water pump.

fluidampr crank pulley is interesting and some “theories” say the increased harmonic dampening especially in higher rpms reducing energy loss from reducing vibrations. Also it is supposed to be a better dampener then stock so should be safer.

Mostly the benefit is just overall static weight reduction. I see a good .1sec increase/decrease in 0-60 per every 1/4th tank gas I have meaning 100% full vs 1/4full from weight reduction is about .3sec quicker.