2003 audi a4 hu

I've just bought new hu for my 2003 A4, i've bought the right harness(metra w/rca), i figure not all the wire's are right, the ACC(red wire) do not match the stock harness, i've search a lot of site, no luck, all they are saying are run the wire fromt he fuse box or some even said form the 75x, what are them, if i need to run off the fuse box, which fuse, there is no acc said on the box, need help

Audi's and VW's often do not have accessory behind the radio based on the year. You will have to locate an accessory wire under the dash, with a meter.

On the harness you bought, there is no accessory? Some of the Euro plugs have the accessory and constant switched. 

the harness that i bought have the two wire but from the car, there only constant wire, no acc even on the stock harness.  they don't have acc which was said by a lot of people in the forum and they use a some kind of of bus cable now