Cruise can’t be done

I hope one can help me, I drive an Audi A6 4B 2.5 TDI 150PS Bj.05.98 and have retrofitted a cruise control unit and drove into a workshop to allow it to be unlocked. Everything worked out so far only that no current arrives at the cruise control system and the mechanic said that behind the engine control unit a large white plug sits with the 2 cables missing, no.9 and no.10. Now I hope that someone knows which cables are missing and how to replace them. I was told that you didn’t have permission from Audi to install or repair such a thing. Please help me. MfG. dasmotiv