That was going to be my next recommendation to check the bank1 O2 sensors making contact with anything. You don't really need your downstream O2 sensors since they only detect catalyst efficiency and alert you to inspect the cats. Since you don't have cats and presumably no emissions testing/inspection in your state, you can disconnect them. Downstream O2s do absolutely nothing for your air fuel calculations so they're safe to disconnect completely. If you don't have room for the upstream location, you can simply plug your downstream O2 sensors into the upstream harness plugs to replace your upstream sensors. Just make sure that the downstream locations are still within the primary tubes or at the collector. If it's too far downstream inside of the Y pipe, it won't work. Again, all the sensors are functionally the same, the only difference is their pigtail length. I have been driving without anything plugged into my downstream sensor harness for almost a year now. I have an O2 heater circuit CEL for those sensors, but it doesn't affect performance one bit.