Wiring wideband to ECU
 

Hi, does anybody know where does the wiring from innovate wideband exactly goes to the ECU, and what part of it?

It doesn't. You need to grab a header with an extra 02 port for the Wideband sensor. Then you run the sensor to the gauge provided in the kit

Edit: Or have a shop weld in an extra bung into stock header.

Are you wanting to tap into the rear o2 sensor for data logging purposes?