Originally Posted by semtex

Agreed. But where I do think more power can result in greater efficiency is that for any given rate of acceleration, I don't have to use as much throttle now to achieve that acceleration rate as I used to. The trick, of course, is in whether or not one has the self-discipline to not use the additional power/acceleration that is now available. I personally do not. I don't really see the point of spending all that money to increase my car's power if I'm not going to use it. Indeed, what motivates me to mod my cars in the first place is that I always want more power. (It's a sickness, really. 'Quick enough' just isn't a concept that I can grasp.) If increasing fuel economy were my objective, I'd have traded in my Z for a Prius and started driving around like one of those annoying wanker hyper-milers. But, having said all that, I have noticed a slight improvement in my average mpg, by about 2 mpg. And I guess that makes sense, as there's no way I can drive the way I want to all of the time, due to traffic, weather, police presence, etc.