Does anyone knows anyting about the effects of changing the underdive pulley? I heard you can pick up an extra raw 8-13 HP! Just wonder what else it will do if anything?

 

don't get the main crank pulley... i found this out from the others

Toyota engineered their main crank pulley to balance the engine and it has a balance weight in it...
the upgraded pullies do not, and they WILL cause your engine to wear prematurely especially revving to redline

the other pullies are fine like A/C or the alternator but they won't help much