Swap, I have driven both Auto and Manual 4A-GE 20V, Auto is good only when you turn on the Power mode where it will allow you to rev up to 7500RPM. For a good Auto 20V setup you will need:
- 2.25" Mandrel Bend exhaust pipes with S-Flow Rear Muffler
- Fuel Pressure set to 34PSI Idle (44WOT)
- Light Weight Engine Oil (0W30, 5W30, 10W30, 10W40 or 15W40)
- Good Auto Tranny Oil
- A very clean Throttle Bodies and Idling Valve
*** AND MOST IMPORTANTLY! as EG9 has mentioned, a healthy engine ***
The way you drive will also determine how "powerfull" your Auto 4A-GE can be, don't be shy to floor the pedal when you need speed because 20V is still a High Rev NA motor anyway, and power will always be there up until 7500RPM shift point (1st, 2nd & 3rd gear)
You can also opt for Adjustable Cam Pulley, but I personally believe that keeping the original VVT Pulley is a better option for Autos. Mild Cams are also recommended and the most likely setup would be to use 264/8.0mm Intake, 256/8.0mm Exhaust combos for superior response and midrange powerband improvement. But these things are not cheap.
And another one as 4AGZE mentioned, Bolt-On Turbo laaa, sure very nice one.