O3GMC

I'm trying to figure out why my 'dynotune.org air/fuel nitrous cutoff switch+guage' is reading too high off my o2 sensor. It is reading 1.18V while my Predator says .920 (purposely rich nitrous tune). The predator is obviously the right voltage while the guage is way off. A voltmeter says the same as the guage.

Could using larger guage wire to splice into the o2 signal wire be giving me a .3xx mV difference?

Thanks for any help