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.
Phil D.