You sure that its "bigger" than stock? I dont see how bigger would help, considering the fact that a bigger pulley would require your engine to work harder to turn (think torque equation, backwards, as well as an increase in rotational inertia)

I have an underdrive pulley on my eclipse. It's considerably smaller (about 1/3 the size) and MUCH lighter than stock (7lbs as supposed to ~20lbs). Effects- rev up easier and faster, accessories dont drain engine power, and ~8 HP to the wheels.

For my car, this was a GREAT mod to do. There is a lot of potential for damage, but I've never had any real problems... and I installed it myself. I did need to change out the belts (the ones they sent with it were crap), they were squeaking pretty bad. Some others I know have had dimming lights when they were at a stoplight, but a little rev quickly took care of it.

Many posts on this board dont seem to like the idea. I'm not aware of the actual level of benefit it will provide for an H22, but its definitley not a modification that you should specifically avoid. If done right, it'll last you 30k+ miles... like mine has already.