issue is more of what the car can do in the "real world" against wind resistance vs. someone's calculations of a mechanical top speed at redline in fifth gear. Also depends on the horspower of the Z. A HIGHER horsepower Z could expect a DECREASE in top end after Leader gears, assuming the car is hitting the rev limiter before and after. A LOWER horsepower Z that can't make redline in fifth because of weight and resistance would expect an INCREASE in top end after Leader gears, since the car would then have the gearing to hit the rev limiter. Clear as mud?