Concerns about pulley's

[Black_griffin6]

Hey guys,

I've recently been doing a lot of research about the lightweight pulley's NST offers and how they might affect my Yaris. From what I can tell, they replace the OEM pulley's with a strong lightweight pulley that reduces weight and allows the car to rev better.

Sounds great...right?
Well from i've also read is that the stock pulley's are weighted a certain way to balance the engine, and by replacing them you're running the risk of greatly reducing you're engine's life.
I believe that has to do with a Harmonic Balencer? (Correct me if i'm wrong.)
I've also seen a few threads about the water pump dying shortly after installing these pulley's, though i'm not sure if that's related because I hear about water pumps going bad all the time.
Anyway, I would like to eventually get some of these lightweight pulley's, I mean they sound really great and i'd love to reduce some weight and free up my engine...But not at the risk of doing some harm to it.

So basically, i'm concerned. Some people say it's fine, some say don't do it, and since i'm not a mechanic by any means...i'm stuck.

What's your thoughts/opinions?


EDIT: I just did some more reading, and i'm reading that accessory pulleys (AC, alternator, ect) are fine to use just not the crank pulley.
Not sure if that's true or not either. XD