I just got done filming a video on installing an aftermarket Heads Up Display in a Fiero which also included a tach display. If only the video were finished editing it would have been something to check out. I'm not at home at the moment to check but I believe if you removes the rear trim from the gauge cluster you'll see a connector plugged in directly behind the tach location. You'll want to locate a solid white wire. I can get you the pin location when I get home if no one else chimes in beforehand. That white wire is the tach pulse wire. You can also tap any pink with a black stripe wire as your ignition switchable power wire.
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