The first task at hand is to figure out the factory trigger sytem. It uses a crank and cam sensor with VR. The crank has 6 teeth and the cam wheel has 7 teeth.

Supported, see InputTrigger/SubaruTrigger

Here is a photo of the cam wheel:


Here is one of the crank trigger...



Center of the circle approximately:

So crank seems to be 4*90 deg, with 2 added tooth placed 32 degrees (measured with gimp).

Requires some code, but firmware load should not be high at all. Definitely worths to code it (better than changing wheel or addon HW).

This might be the same trigger setup as the North American Impreza 2.5RS (at least for the 2000 model on Phase 2 SOHC). Service manual for that car shows 97, 65, 10 BTDC per bank on the crank wheel. Cam wheel shows 5, 27.5, 50 ATDC #1, 20 ATDC #3, 20, 50 ATDC #2, and 20 ATDC #4.