LOL at some comments Id say if youve never used one, dont guess just to reply

Ive had a few cars with very much lightened flywheels, and some have more effect than others, but it just makes the car feel more lively, hard to put it in to words really, but if youve driven a motorbike compared to a big non turbo diesel and youl know some engines feel lighter and more revvy than others, well lightening the flywheel makes it feel closer to the bike.

Never had one that made the car feel worse in any way on the road though, nothing noticable on a modded car which has a lot more things to fuck drivability, like big clutches, big wheels, big turbos, whatever.

Wether its worth the cash on a Cossie i dont know (i expect Markk can tell you that), but at least my reply is relevant