i got an A/T too and i put it in D mode whenever i want to hammer it. this way, i don't have to worry about over-redlining the car and it shifts just before it hits the redline.
one thing less to worry about...

 

haven't tried this yet...but i've heard the grounding wire kits take the shift lag out. I don't know how valid that is, but they are fairly cheap to try ($50-70 maybe). I highly recommend a POP charger or K&N cold air intake...or cheapout and get a z-tube.

 

I have:
Z tube, K&N drop in
Crawford Plenum
Heat resistant lower plenum gasket (I forget the name of the company)
Crawford Cats
Fujitsubo Legalis-r w/ Y pipe
Stillen Engine Dampener
Grounding kit
Technosquare L-spec reflash

I'm right about .2 sec or more faster than near stock Gs and Zs that I have run against. Actually there is only one guy out here with a heavily modded track model Z (normally aspirated) that can consistently beat me. But he can really power shift well, no way for me to get around that.

This is just my experience at the track, your results may vary.