I recently bought a aftermarket tachometer for my 91 3000GT it was used so has no instructions, it has 4 wires.. 1 red (power) 1 black (ground) 1 green (unknown) and 1 yellow (unknown) does anyone know where those two wires would connect, the car already has a tach it is just inoperable at the time, i think its just the gauge itself..any information would be helpful thanks!  

by the way its an SL non turbo, if neede

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tunrace411