I am not sure that you fully appreciate the affects of gearing, and seperately the nature of the relationship between torque and power and rpm.
i.e. its is torque times rpm that accelerates a car.
Torque is not what accelerates a car, it is how many times a second it is transmitted, i.e. Power that accelerates a car.
Obviously being able to utilize a lower gear ratio has an affect on acceleration, as I said up to 20%.
This means that a race driver will always always chose to change up past peak power (even if there is no corner
..for the higher gear to be quicker it would have to overcome both the 20% difference in gearing, and the drop in power as compared to the lower gear. The car isn't going to drop into a higher gear gear at just below peak power, far, far from it.
(If you dont get this bit and wonder why you would want to rev the car out to its limit, try thinking about what gear ratios mean a little more)
Here is a 3.2 v6 power graph from RotoTest.
Google Image Result for http://www.rototestinstitute.org/spec/view/png/graph/STR-05091501-kW-Nm-C.png
As Skip Barber says "There has been a lot spoken about when to change up a gear, but the truth of the matter is simply that one line covers it, 'change up at the red-line!'"