Ahh, so you're piggybacked into the stock tach signal. I don't know anyone successfully doing this on the v3 board because of the noise you get.

Before I converted mine to a standalone and had the crank sensor's 3 wires go straight to the Megasquirt I couldn't drive the car over 2200 rpms, without loosing the rpm signal to noise.

You think there's anyway you could get your hands on a scope to actually take a look at the crank signal at the megasquirt?