The immobiliser will be interesting too.

I've got detailed wiring diagrams and system documentation for Toyotas of the same era with TVSS but not the MR2.

There is a belief that on cars with the later immobiliser

(ECU ends 550 or higher) that the ignition key is paired with the ECU.

I've seen this in a number of threads on this forum for example.

However other TVSS cars have an immobiliser ECU somewhere in the car which is the part paired with the key.

The inductive ring in the ignition barrel picks up the transponder in the key and transmits that via a signal amplifier to the immobiliser ECU and if the immobiliser ECU is happy with it it sends a continuous pulse signal to the ECU to say

"all is good, continue running".

Take the key away, signal stops, engine stops.

I know the TVSS MR2s have an immobiliser ECU so I suspect they work exactly the same way and that the ECU is not tied to the ignition key at all.

We shall see
