From an article I read, reducing unsprung weight (i.e. rims and tyres), it reduces the rotational mass and moment of inertia. They claimed that a 5lbs per rim reduction in unsprung weight was an equivalent of 200lbs reduction in sprung weight. That's a 10x effect increase. So going to the 6.7kg rims from the 10kg stock rims will be equivalent to a 132kg reduction in sprung weight. That's better than pulling out your interior, putting on a carbon fibre bonnet and removing the rear seats and spare tyre.
Also, the same 10x enhancement effect applies to other rotational mass such as the flywheel and crank pulley.
http://hondaswap.com/general-tech-ar...art-2-a-29058/