YZFMax

Agreed, using the IGN would make sense and that is why I was also a bit confused, thus asking Silvermine the question. I did end up wiring it up as per their response. I've been using this for since I installed it back in 2020 and had no issues.

Also check your fuses. One of the connections to the glass fuse was not making a good contact causing the dash lights to go out. Had to tighten the connectors a bit and it resolved the problem. And if you removed your dashboard recently, make sure all your connections back into main harness is snug.

The tach wire is used to give the signal to the power steering unit to turn the unit off when the car is turned off. This is what was explained to me when I asked Silvermine this question. I'm assuming IGN would be used to power the internal relay in the unit? So you would need both of them to be wired in correctly. As per my pic above, I tapped into the back of the tach gauge to get the RPM signal. It all worked out for me very well.

I recently installed the power steering kit, one of the best mods to date. The car is much more drivable now, and have no issues at highway speeds. I ended up using the GPS sensor instead of the speedo potentiometer that came with the kit. Had no issues with the fitment on my 260z (uses the same unit as the 280z), it lined up perfectly in the location of the manual rack. As for the tach wire, I made a splice and attached it to the red/black wire on the tach itself. The signal is basically used to tell the unit when to turn off after the car has been turned off, so it doesn't drain the battery.