Anyone have any experience with these?

[blocke]

http://cgi.ebay.com/ebaymotors/BMW-E30-325i-is-ix-ic-87-91-Light-Weight-Pulley-/230484226074?cmd=ViewItem&pt=Motors_Car_Truck_Parts_Accessories&hash=item35a9ee301a

I guess the theory is similar to a lightened flywheel. Less mass for the engine to get spinning.

Yes or GTFO?

[E30Gus]

Cha Ching....Hell no
I think it would be the difference between getting your FW lightnened to 12.5 lbs instead of 12.00 lbs. Besides if you are worried about getting rid of junk for some extra power you would also get rid of your AC and PS(notice pulleys for belts).
My 2 cents on the aformentioned product = GTFOH
Word

[jlevie]

Deleting the power steering pump will make more difference than lightening the harmonic balancer. Then there is the issue of what effect that might have on the bottom end bearing. The harmonic balancer is called that for a reason.

[blocke]

I figured they were shit, since I havent heard anything about them from anyone before. On another note, how about underdrive pulleys? I know they are a big thing in the Honda world..would getting bigger pullies for the alt. help any?

[jlevie]

Again, not as much as removing the power steering pump.

I have a friend that has substituted a larger alternator pullel on his race car to free up a bit of power. It works, but the alternator won't charge the battery below 2000rpm. You'd have to go that far to gain a measurable increase in power.