I have a S4 chassis that was originally an A/T setup that was swapped to a M/T in the past.
The vehicle was a wiring disaster that I am slowly rectifying. Today I got the Reverse switch wired in to the chassis so the Reverse lights work.
What are the other 2 (Green) wires coming off of the Reverse switch?
Everything I can look up shows to be for the 5th gear switch. What is the function of the 5th gear switch, and where does it connect to on the chassis harness?
I don' see any solid Green wires on either the S4 or S5 wiring diagrams.

Does anyone have a photo to share of their stock wiring?

 

I don't know the specifics of an auto to manual swap so I can't help with the wiring. However, I can tell you that the 5th gear switch is used to tell when in 5th (obviously), so the ECU knows that it can switch to closed loop and use the O2 sensor feedback to trim fuel.

I think it also tells the ACV to switch one of the solenoids or something for an emissions reason. I can look into it after work for you but the info should be in the service manuals & training manual available at Foxed.ca.

Point is, it has only minor fuel economy and emissions functions. It should be fixed properly but don't let it prevent you driving the car if you want to do so.