Since we all know HP is just a mathematical manipulation of torque to create higher numbers for magazine articles.And HP [at a glance] is only useful in determining the highest top speed

One must use torque in any calulations of acceleration, so you convert HP back by multiplying it by the rpm ratio where the HP is presented [5252/6000= 0.87533, 5252/6400= 0.820625~~etc.]

Even though the torque number falls from the peak rpm [4000?]and by definition peak HP is where as the torque falls enough - the gain in the ratio of rpm increase is insufficient to counteract the fall in torque.There is still significant torque out to the engine redline and beyond.

What one has to know is the amount of torque at the rpm one shifts at because the torque gets multiplied by the gears so in every case there is more torque at redline than there is at the torque peak in the higher next gear.

In a 2.78 1st gear a 307 lb/ft [at 4,000] might decrease to 200 lb/ft at 6900 rpm but shifting to 2nd [1.58/2.78=0.568 whereas the 200/307=0.651.......there would be more torque to the wheels at redline in 1st than at anytime after a shift to 2nd.

In 2nd at redline a shift to 3rd [1.0/1.58= 0.6329] is still just below the worst case torque fall off! --- by 3%.

For different engines you must overlay the engine torque curve with the gear ratio curves to determine what is best.

5 - 6 speed manuals MAY? have the gears closer spaced so it might be more efficient to shift at or just above the HP peak but you never know without doing the calulations.

Nuff said Tech. Everybody is so hyped on HP but torque is wha annihilates competion on the line and in midrange. HP is not even fully utilized until the higher range of speed.