Have you considered the Innovate LC-1? I've been running it on my bimmer for about 6 months. Works perfectly. It's a wideband that has programmable output. I split it's output to go to the input of the factory harness. Then use the laptop to tell it what sort of voltage it expects to see. (Might be different for the Z than the bimmer). I tried non-foulers and O2 simulators and was never able to get it to work. This did the trick. I also run a pair of resistors to simulate the heaters. No CEL for 6 months.

 

Brillo works just fine. Just have to change it out. I need to hit up a bunch of sinks for some of the screens.

 

One of my O2 sensor, the lower one, one that connects into the CAT was ripped off recently. My workshop's solution was to removed the remaining one totally and turned it off from uprev. So my test pipes have no O2 sensor on them anymore.

He said the lower O2 sensor is not required.

However, I feel the car seem to be behaving differently now. Can someone advise pls.