ok i know they give you a much more accurate reading for tuning. But i still don't fully under stand how it fully works. Does it take over the function as the original 02 sensor with better readings or does is it just for tuning purpose to get a more accurate tune?

It is for both. Use it for tuning, on an as-needed basis, or hook it up permanent and use the simulated NB output to signal your ecm. Search for different WB 02 sensor setups and read the manufacturs info for each one.

The narrow band oem, stock, sensors are *switches*, the only are meant to be accurate as far as telling rich or lean of 14.7:1. That's it.....

A WB on the other hand, is designed to read in a linear fashion across it's output range, and give an a pretty fair indication of what the exact AFR is.

Ads mentioned, reading thur the various online brochures will tell ya which can WB has a simulated narrow band's output, so it can talk nice to the ecm..