So I recently installed an AEM UEGO Wideband Gauge and immediately noticed a very audible ringing noise whenever it was on. I did a lot of searching and found a lot of people having the same problem but found only suggestions to run power and ground straight to the battery which did not fix it. I finally came across an old thread where someone suggested using a capacitor right next to the gauge and I am happy to say that fixed it almost completely. It still rings a tiny bit, but you can only hear it if you are listening for it. Per their suggestion, I used a 2200uf, 25V, Low ESR capacitor and soldered it in line with the gauge. Figured I would post this for anyone else who is having this problem to find.