Testing Automotive ECUs

That's pretty cool. Reminds me a lot of the Megasquirt setup and the Stim board they offer. I know you've already put in lots of work to your own parts, but I've seen other people use the Stim board as a standalone signal generator for other purposes. It's built with the Megasquirt in mind, but all it really does is simulate sensor outputs. It can simulate missing tooth sensor wheels as well from what I understand, so you can do work on sequential style systems. When you think about it, and EFI system is really pretty simple in a certain sense. Read in some sensor data, do a calculation, and output a control signal that fires fuel/ignition. Doing it all in realtime and fast enough to deal with high rpm is the challenging part.