Its my understanding with some tweeking too the tack settings in HP tuners I can get my gauge too work without having the power wire in line..

I was wonder if anyone has nailed the settings down and made theres work, my cars a 89 Formula..

 

Changing the tach output from 4 cyl (stock LS1) to match a V6 or V8 tach is in the tune

All firebirds require the booster wire for the factory tach. Locate the 12v IGN and tach pins on the PCM. Tee into both connecting them with a 680ohm resistor inline. Resistors can be found at radio shack in packs of 5 for a dollar

Rule of thumb for tachs:

Wrong tach value, change it in the tune or repair the tach (camaros)
No tach, needs a booster wire