Dpaz, eddscott and wigandill - Just a case of swapping a few wires out. As i found the TT harness connector won't fit onto the B7 slip ring so this is why we need to modify the B7 harness using some of the TT harness wires. Took me a while to work out actually how to remove the wires but finally got there. In the harness connector theres a purple plastic 'pin' which holds each connector secure, however once you remove this each wire is still as solid as when the pin was still in! So after some playing, an hour later i found that you need to use a pin in the bottom of the connector and wiggle it in the small slit in the middle of the harness. Haven't really explained it very well but i've left the old harness at my parents so will show you once i get it!
As for where to put each wire:
The slots are numbered on the harness
3 through 6 are for the airbag - DO NOT TOUCH!
Remove each harness from the airbag.
You'll want to remove all the insulation cloth tap on both harnesses as we need to remove some cables. The earth and horn crimps are different on the B7 harness than the TT harness. This is why we need to swap these cables round.
Firstly lets start with the A4 B7 harness. Remove these cables from the A4 harness
Brown (Ground)
Yellow (Horn)
Also remove all the wires in the harness which go to the steering wheel controls (They're all black, don't get confused with the airbag ones! you'll know if its airbag because each airbag connector has twisted pair wires). You will not be using any of the wires removed from the B7 harness.
The B7 harness is now ready to take new connections
Now on to the TT harness.
Remove the:
Brown (Ground for controls, Horn and airbag)
Yellow (Horn)
Red (Controls)
Purple(Controls)
Now you want to use these wires to fit to the B7 loom connector, Put them in the correctly number slots as below.
This is where the wires are to go in the A4 B7 loom.
Brown to 1
Yellow to 2
Red to 8
Purple to 9
I had some cloth tape to wrap the harness back up as you don't want any wires (especially the airbag) wires to get snagged or chaffed.
Once the B7 harness is ready, fit it to the TT airbag ensuring the horn and both ground spade crimps are on the correct connections.
Hopefully i've explained it so its understandable. I can always take the bag off to show you everything, should have got more pictures. But any questions just ask. If you're scared can always send me your harness and i'll do it
A4_MaJiK - Currently i'm not, but it could change, you'll be the first to know
AudiB7Jay - I believe the standard audi sound system used the headunit to power the front speakers, and a rear amp to power the rear door and parcel shelf sub. The Bose system which i have has a dedicated amp to power the whole door speakers and the sub so i had to a harness which turns the headunits outputs into red and black RCA outputs. I also got a canbus adaptor which turns the canbus computer signals into a switch 12+ so it turns on and off with the ignition and accessory position of the key. Also it allowed me to keep the MFSW controls so i can control the volume and change track! Only issue i have currently is i'm getting a hum when i turn the lights on! noise canceller should sort that.
Can't remember where i got the kit from but will have a look for you, quite pricey, in the range of about 70 pounds.
solaris - Pretty easy, just remove the 3 cap heads and it comes out. To get the polybush back in i had to remove the housing but thats only 3 bolts so really simple. Some people haven't really noticed, but the engine/gearbox/gearstick was tilting back when i booted it, so took the plunge, had to get it from the states, haven't noticed the stick moving anymore (y)
eddscott - It's a mount on the front of the engine, stops the engine tilting back aggressively under heavy acceleration.