i have read that on this model there is not a really an appreciable difference in gas mileage, i know it is for keeping the gases wihtin the manufacturer range... but usually it improves the fuel mileage since without it (the o2 sensor) the system by default would set to a rich mixture...
after installed the new o2 sensor, the check engine light went off and the mileage increased by 0.6 or 1mpg (several method to measure)
but i wonder
please, check the image

i know the sensor should be installed like the no. 1 example
BUT mine (after relocated, because this vehicle had catalitic removed)
the muffler guy installed like the no. 2, he told me that the o2 sensor does not need to be in "full" contact with the gases, that only needs a "little" doze of the gases in order to make its job....
not too satisfied with this, i wanted to ask you if i should go back to the muffler shop and make him to desolder the o2 sensor socket again and to make him to solder at its correct level so the part of the o2 sensor that must be exposed to the gases is fully exposed?
just like the no.1?