I remember that it was 20% underdrive for the Unorthodox and 30% for the AFX. I got an AFX, I don't really notice the horseys anymore cuz I guess I got used to it, but it made my car more responsive and should make your engine last longer. I had problems with my belts squeking apparently on my particular eclipse the belt was too big so I bought one that was smaller. Well I'd suggest getting the AFX...
http://www.hadesomega.info -car specz and movies 95 Eclipse RS | 76' 280Z | 89' MR2 | 99 Neon | 91 Zephyr Who sez FF can't drift?