As with any low voltage electronics, lots of ppl have had interference problems. Thats why toyota uses a shielded wire from the O2 to the ECU. I recommend you use a shielded wire for the O2 pickup to the gauge too. Radio Shack (if you have one near you) has a 22g single conductor shielded speaker wire that works perfect. Also to consider if interference is still a problem (was for me), run an isolated power circuit to the battery with a relay on the ignition circuit. Set up like this all is well. Good luck.
Thanks for the info guys. Hopefully I'll be able to figure it out.
So in order to adjust the mixture, would I just turn the little screw on the AFM? My friend has adjusted it before but we never had an A/F guage.