aftermarket stereo wiring harness

[Momoko]

Hi all i'm new here.. I want to install a DAB pioneer single din head unit in my B7.. ive bought the extra harness, i don't have bose or steering wheel buttons and just have the concert single din in there at the moment.

Can someone tell me what that yellow wire thats not joined does? also do i have to switch over the other yellow and red wires over? my MK4 Golf I had to switch those over.. wondering if its the same thing on this car.

 

Thanks

[Momoko]

Anyone?