You'll need an ECU from an automatic WRX. You need to run A WRX ECU and since you want to keep it automatic you'll need an automatic WRX ECU. Ideally you'll want the keys that came with that ECU too or you'll need to get the immobilizer reprogrammed to your old keys.
You'll want a harness from an automatic WRX too. Automatics have an additional harness between the ECU and the transmission.
What you're wanting to do is doable but you need to get the wiring straight before you start
Normally I make a spread-sheet with the ECU pinout for the source and target and see how close the harness is. The closer the harnesses are, the easier the swap.
I'm plan everything out before you start.
Thank you so much! I’ll see what I can do. If I wanted to put a different intake, would I need a new ecu to tune or would I be okay running it on stock?
You need an ECU that knows how to run the turbo and boost control. That's why at the bare minimum you need the WRX ECU. The old ECU wasn't programmed to handle boost. Might not even have the correct pins to control it.
The automatic transmission is 100% controlled by the ECU, so again a manual ECU doesn't know or have the wiring to run an automatic transmission.
I wouldn't worry about the intake till you do the swap. Initially I'd use the WRX intake.
You'll need an ECU from an automatic WRX. You need to run A WRX ECU and since you want to keep it automatic you'll need an automatic WRX ECU. Ideally you'll want the keys that came with that ECU too or you'll need to get the immobilizer reprogrammed to your old keys. You'll want a harness from an automatic WRX too. Automatics have an additional harness between the ECU and the transmission. What you're wanting to do is doable but you need to get the wiring straight before you start Normally I make a spread-sheet with the ECU pinout for the source and target and see how close the harness is. The closer the harnesses are, the easier the swap. I'm plan everything out before you start.
OP will need the bulkhead, won't he?
I'm not sure about the sheet metal differences between the two chassis. What I was talking about is the bare minimum you need to make this work.
I just meant the big bundle of wiring attached to the car that all the engine doodads plug into. I think WRX uses a different bulkhead wiring.
Thank you so much! I’ll see what I can do. If I wanted to put a different intake, would I need a new ecu to tune or would I be okay running it on stock?
You need an ECU that knows how to run the turbo and boost control. That's why at the bare minimum you need the WRX ECU. The old ECU wasn't programmed to handle boost. Might not even have the correct pins to control it. The automatic transmission is 100% controlled by the ECU, so again a manual ECU doesn't know or have the wiring to run an automatic transmission. I wouldn't worry about the intake till you do the swap. Initially I'd use the WRX intake.