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 2.6 Pulley/Idler l Airaid l o/r X l 305 NT555R's l Recaros l
04 Azure Blue Mach 1 / 03 Sonic Blue 3.8 / 14 Sterling Grey F150 FX4 402A 5.0 / 11 GT500 R.I.P.