Correct me if I am wrong (usually am)
but the lightened / balanced flywheel should help you rev up quicker,
but not actually improve HP. (Had a 10# one on my 98 8v GTi)
After I put it on, my 2.slo felt like a crotch rocket!
For the top end, you really want the momentum (rotational inertia).
A friend put one on a vr6 turbo, and felt like it hurt his pulling power.
The motor revved down so quickly, he was losing boost in between shifts.