I'm not sure exactly how you'll do this but you'll need to:

- Read the file from the car (using nefmoto flasher if me7 ecu, for other ECu's you'll need different tools)
- It's handy to get a read of the EEPROM before you do anything as a backup if something goes wrong.
- Once you have the file you need some software to edit the file with (WinOLS or tunerpro seem to be most used on here)
- You'll need a definition file which is like your contents page, a list of the various maps/tables. (Called XDF (for tunerpro) or KP file if used in winols. there may be one floating around on here you can use when you know what ecu you have)
- Then make said changes to delete the rear 02 sensor.
- You'll then need to correct the checksums since you have changed the file (DO NOT skip this step or you'll end up like I did with a bricked ECU and without the know how to sort it myself)
- finally when you've done everything maybe post the file on here and ask for someone to double check its ok.

Do a lot of reading also. I've no idea what ECU this car uses but if it is me7 then read the s4 tuning wiki thoroughly. A lot wont make sense at first but stick with it and just keep going back to it as eventually it begins to stick.

Hope that helps. I have been a bit vague but trying to save a fellow noob from making mistakes I did.