I had another idea while sitting here trying to figure out WTH is going on. What about adding a couple diodes to the signal wires? Maybe the problem isn't a surge in but a surge out. When I am turning car killing engine maybe the injector or vss is looking for a ground and the Guino is there to provide it for it. Just add a couple where I have the arrows to. dcb hope you don't mind me using your schematic image.
