Racing...

If you leave it in auto and floor it, there is a delay while the car downshifts. If you were street racing, which i wouldn't recommend, you will surely loose a couple of car lengths depending on the other car.

While at the drag strip, it pretty much reacted the same way whether i left it in full auto or put it into first and then i let it shift on its own. Roll up to the staging line, wait until the yellows begin to roll down (assuming your in test and tune tree). As the lights roll down, while holding the brake pedal with your left foot, begin to roll on the gas until you get right around 1,500 - 1,800 rpms, if you time it right, you will react those rpms just as the last yellow flashes. Simply side step the brake pedal and roll onto the gas. I netted 13.33 @ 102 mph 3 weeks ago, i'll be going to the race track again this weekend with my club.

As for at a HPDE (road course), i've never tried it.

As for Autox, well i'll let you know soon as i'll be autoxing my "6" sometime soon. But i would imagine you would shift and leave it in 2nd gear as it appears to be the right gear and speed for most autox courses.