Thanks for that Cliff, its a handy idea that will overcome the stumble that some get when we use the spark retard/cut features for idle control.
Onto RPM... Its a case of finding out what the stock Nissan ECU uses, with most of the cars I've done we've been able to use a feed through a small diode network to give the tacho the trigger it wants. I see that the Nissan RPM count comes from the ECU so I'm thinking that we're probably going to only want to give the gauge +5v pulses. I've put it on my to-do list and I'll get looking later today.