from what i've read, changing pulleys are not the best thing for your car (there was a technical post from dinan here a few weeks ago that really educated me). i installed an 11 lb aluminum turner motor sports flywheel in my supercharged 328 and it made it awesome. you get vibrations that the heavy flywheel used to absorb but they are kinda cool. really quick acceleration. i did mine along w/m-3 clutch setup - huge improvement and i think it's less damaging to the whole system than the pulley changes.