...
And in terms of performance, driveability? Noticeable changes?

 

driveability, no. Performance, it did make the engine want to rev a little faster. I forget the exact weight of the stock pully, but it was a couple of pounds where as the underdrive was less than half a pound.. and right where it counts too.. in rotating weight

 

My headlights dim a bit, but when i had my system it powered the amp just fine on idle, sure if i were to sit on idle for a few hours it might drain the battery but that shouldn't happen lol.

Check my DIY thread (and the weight reduction thead) for details on weight difference and before/after reactions.

Definitely worth it..

 

Exact weight of both:

Stock pulley 1811g
Obx pulley 396g

 

I like the one I got from Col. That thing is great. Havent had it on yet but its super light. I cant wait.