Tach issues

[XLexusTech]

HI I have an LS3 PSI harness and an auto-meter electronic tach. The tach is a special addition 2006 Gm Performance parts issue that I need to keep.
I mention this because tachs pre 2007 are known to have a problem with low voltage signals.



Tach is inoperative but is fine on a bench test. Found lots of info about using a step up resistor inline. Then found so much conflicting info.. Mus use 12v.. not must use 5V... must use 1Kohm.. no us 5K ohm. that I got really worried.

So I went out and bought autometer 5117 https://www.autometer.com/tach-adapt...E&gclsrc=aw.ds

question has used this tach adapter? Instructions say tap into each coil bank.. which I am not doing..
I want to use the tach signal (white wire) out of PSI harness

Alternatively If someone could set me straight on the step up resistor that would be helpful as well