Ok...so I've researched further. I'm sure you've all heard of the apexi RSM.....? Anyhow...this gizmo has a wiring diagram for the nissan march which tells me to splice the wires for vss, ground and 12v directly at the ecu. As this is a universal gadget also used in mr2 I'm certain the vss signal must be as strong as the mr2 signal ;-).
What about the following....up until now i pulled ground from the chassis close to the instrument panel. But maybe that is the problem, maybe i need to pull ecu ground? Is that realistic?
