I'd say it's better to leave it to the computer
However, the stock tune in the computer sucks...you can buy a tuner and make the upshifts and downshifts more aggressive and solid.
Or you can buy a B&M Hammer Shifter for your auto...this will allow you to manually upshift and downshift thru each gear, basically like a manual without the clutch.
12 Black GT500 SVT PP l VMP TVS l JLT123 l O/R X l 28x11.50Rx15 M/T Street R's l BMR Suspension l Recaros
03 Sonic Blue 3.8 / 17 Magnetic Fusion Sport 2.7 EB