New 370 owner (first non 4 cylinder car)

[wilsonp]

Unless you practice (a lot) on acceleration runs, I think you'd be faster leaving it in full auto. Even though the shifts are (supposedly) a little slower, the car should always shift at the best time when you are at WOT.

I generally use manual modes in AT for when I am going at a slower pace and the auto wants to shift up when I know I want more throttle responsiveness (say, getting ready for a two lane pass) or engine braking (not too often) or accelerate after a turn (downshift before the turn, rather than have the AT auto downshift during the acceleration out).