Would anyone be so kind as to point me to an appropriate post with mention as to the location of the ECU in a MY99 Impreza Turbo? I understand its somewhere in the passenger footwell? How do I get to it?

btw - the search function is u/s otherwise I'm sure I'd have found it by now

erm - think I've found something pointing me to under the carpet in the passenger footwell. Is this right? If so, which corner, or where should I begin to peel back the carpet?

*bump*

The ECU is under the passenger footrest/bulkhead.

On my MY93 WRX, there are a couple of trim clips which need to be unscrewed/popped out on the plastic next to the door. This makes pulling back the carpet a *lot* easier.
Carefully peal back the carpet, and on my car there is a protective cover, retained by 4-off m10 screws.

Under this cover lies the ECU and the wiring loom.

I would guess the MY99 ECU could be got at in very similar fashion.