Looks like you suffered from the "Hey-I'll-install-this-cuz-it's-cool-lookin'-even-though-I-don't-know-what-it-does" syndrome.
Did you even read the info that comes with the gauge (Autometer explains how these things work).
Rather than explain what/how and A/F guage is or how it works I'll just post this:
http://www.gadgetseller.com/gauges/techinfo.htm 
