Do you think measuring the time between TDC signals from the opti for each cylinder would be useful - say to 16us precision? It's one of the items on my DIY-LTCC todo list, specifically for this purpose. I've also been thinking about the possibility of plotting angular velocity using the high resolution signal if the mcu is fast enough to handle it.

Mitch - you wouldn't need to be using it as the ignition system, it could be plugged in between the opti and PCM at the 4 pin connector on the side of the intake.