The mere(?) 20 extra horsepower stictly comes from ecu and better breathing. The motor has not been tweaked in a major mechanical way. The extra horsepower only shows up at the peak, which should not dramatically affect the acceleration. The powerband has not changed much given that the majority of torque is available from lower rpm. However, the gear ratio does increase the performance. Shorter and closer gear ratio means you have more torque available than wider gears in low to mid speed driving, thus the throttle to be more responsive. Because the first gear hits 60mph, you spend more time driving with less torque in lower speed. On the other hand, with shorter gear, you have more accessible torque at the same given velocity. Theoratically, unless the vehicle is driven above 90-100mph, contrasting vehicles of 04 and 06 will be noticeable in terms of acceleration. The gas mileage should only be effected by the way of driving. What it means is that if the vehicle can travel 50-60mph in first gear, one can be lazy not to shift and drive in higher rpm. with shorter gear, one must upshift, lowering the rpm, thus conserving gas. Total saving mpg must be 1+,- mpg at the most. I do not own gallardo but i have driven 05 and 06 multiple times. in my conclusion, the both cars drive the same on the freeway. In locals where i travel less than 100mph is where the 06 models shine. The 06 feels like 05s with the imaginery 'sport' button on. I find taller geared 05s better car drive in the twists because of the taller first gear, where i could hit corners hard in first gear with my rpm in 6-7k range. With 06 models, i either hit the corners slower with first gear or faster in second gear but with much less torque than being in high rpm in the first gear. If you prefer cruising in locals, then 06 models are definitely better. Otherwise, if you hit the twisties like i do, than 05 might be a little better.