With an aftermarket ECU, you need a wide-band O2 sensor. In order for a wide-band O2 sensor to work, it needs a controller board. Without getting into all the details why, just know that you need to output a signal that varies from 0-5 volts(A narrow-band O2 sensor outputs between 0 and 1 volts and does this without a controller board). The Speeduino can read this voltage and know the A/F ratio and adjust it, this is what's known as "closed loop" A/F control.
A narrow-band can control the idle mixture and cruise mixture, but defaults to open loop when not idling or cruising. That's why it's called narrow-band. Conversely, the wide-band reads all the time and can help with tuning in all modes: warmup, cruise, WOT, decel, etc.
I got the wideband controller, wiring, and a little 3-digit LED display. I may not use the display, I can read the AFR through the app, but for $7.50 why not?
https://www.wide-band.com/WB-D...nd-Kit-p/wb_d1g1.htm
Once I solder it up and verify function, I'll pot it in epoxy in the little black case that it came with.
$47.50 for that, without Bosch O2 sensor, which I already have from my AEM POS that died. I got this a week ago, but forgot about it. 
@Carlos G : this is wired exactly like yours, diode on the red(+12v) lead, and fuse on the black(ground) side.
Total expenditure to date: $247.50