Nope, the '03 has a different ECU than previous years due to the new drive by wire throttle. Besides, putting an '02 ECU into any Celica would cripple it. The '02 is the red headed stepchild of Celicas, since it has a low rev limiter (7800 vs 8400).
The only way to do that is to swap out throttle bodies and gas pedals. You should be able to get the cable driven throttle to work like that, and have PFC compatibility. Hardest part would be routing the throttle cable through the interior and engine bay, if you decided to tackle this yourself.
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