Hi Kur4o!
Re " light goes through the slot it will be 5volts on the line or 1 in digital" : have you measured this ? I ask because sometimes the setup is just a photo-transistor. Light hitting it biases it on or low... I will find this out but a confirmation would save me time.

I find talking about degrees relating to Opti a bit confusing. Wheel has 360 slots...cam runs half speed... each slot is 2 degrees crank (yes??). Counter running to 720 makes sense if both rising edge and falling edge are counted (???)
I have disassembled and commented the calculations for rpm also. Have not yet traced the path between the E and T sides through the SPI. Interesting that the SPI between sides transfers bi-directionally at each transfer.

I have updates for the analog info posted earlier which I will post a bit later, a few more things to confirm.

Conformal coating on the boards is a PIA.

Un-related question for all: There are three driver chips used which I believe are "low side drivers". They are in 23 pin SIP packages, lead formed with an alternating offset. Does anyone have a "bricked" ECM that could lift the part off the heat spreader and see if we can identify the part? It looks to me like this is an octal part driven through an SPI interface. If we can find a data sheet for the part it will be much easier to see the format of the drive and error info transfer.

-Tom