Pulley Kit
 

For example the Tru-Power Pulley kit from AEM, whats it really do? And is it worth it?

Pulley Kit
 

any down side? worth the 170? does it make a noticable diff?

I'd say save your 170 bucks towards a nitrous kit!! Or at least get a good set of cam gears. Pulleys look nice under the hood. For the money they aren't worth it! Maybe 5 hp at most if that!

Yes. There are a few issues, including low alt output from being underdriven, and vibration problems from the loss of mass. No, and no. A lightweight flywheel will reduce rotational mass a lot more, and won't have any significant downsides once you get used to it.

Unless he gets new cams the cam gears aren't going give him too much except good looks under the hood too.

i just installed my pulley kit yesterday and i notice a little difference in power but only from my 2nd to 3rd shift and my punch from a 20 roll. i would have rather gotten headers but those will be in soon newayz.

dimming of headlights etc.. is also an issue with pulleys.. some can tell, otheres cannot.

helps to keep your revs up when shifting, depends on what your looking for if its worth it. if you have I/E/H already, you will notice difference more than if you just do pulleys. i did the crank, P/S, and Alt pulley and i liked it when i was NA, but i also installed lightened flywheel

That goes back to the decreased alt output problem that I mentioned. No, it doesn't. It's actually the exact opposite.