'86 2.5L Tach is way off

The Tach in my MJ ('86, 2.5L, AX-5, 2WD) is roughly double what the motor sounds like its running at. All the other gauges are fine...

I hate Renix crud... some many wires... EVERYWHERE!!!
I have a wiring diagram... but I cant even find the set of wires its referring to, especially since the diagram of the back of the gauges DOESN'T HAVE A TACHOMETER!!


Thanks for any help you can throw at me....

ttt