It could be the rear end too. If toe angle is changing somehow it would cause rear end to go a bit sideways so you have to correct it with your steering wheel. In one of your posts you stated that one of rear wheels was off just after a test drive. Check bushings there. It is not really believable but check if toe adjusting link is tightened. Bolt with marked washer:



Same thing if the rear camber is not properly fixed. It can be adjusted by turning eccentric washers under that nearest bolt in this picture (forget the wrench, it was there for something else):

 

can you post your alignment readings if you have them?

 

Booked to the dealership next week, demanded wheel centering with VAS 6224. I´ll let you know

 

Please keep us posted.

 

Any updates?

 

Some guys would come back only when they need something. I hope this is not one of them.

 

No I´m not, been there yesterday, same story as before, they didn´t charge me however. Been advised to change the suspension arms, so I´m in the process of ordering whole front suspension.

 

So, ordered a new suspension, changed. Nothing. Been to the dealership, they aligned the car, nothing changed (been fined for labor). After fiddling around with the settings, we were able to set the car driving straight in automatic, whenever it drops to dynamic (and speedway mode), the steering is off as it was. When I asked to dealer to recheck the alignment according to the ELSA, along with tools VAS 6224 and VAG 1925 + VAG1925/1 they refused to do it because, i quote - setting the Toe In curve is a special procedure. When I demanded setting the toe in curve, they said they cannot do it because the VAG 1925/1 adapter is unavailable for order. Here are the alignment readings

 

By the alignment readings, your experience is right on the money. In Automatic mode, tour left and right toe is similar so when you go down the road, your wheel is straight. Now in Dynamic mode, your left toe is pretty straight but your right side is towed in slightly. Now when you go down the road, the steering wheel averages the toe so you would have a slightly right wheel. So there is something where your left side suspension changes left toe more than your right toe when in dynamic mode.

 

I'm quite sure you have lower control arm to subframe bushings that are bad.

If the lower control arm bushings are bad, they will cause steering misalignment (tough only a slight one), not like 10-15º usually, unless the bushing is totally gone.

The upper control arm bushings usually start to squeak, and can cause steering wheel misalignment, if they are really bad.

The lower control arm bushings will 100% sure cause steering wheel to shake at high speed braking.

The lower rear control arm bushings are available to buy separetly, cost a few ten euros each.

http://www.ebay.com/itm/Audi-A8-S8-VW-Phaeton-2-Premium-Lower-Control-Arm-Bushings-04-10-/181168119903?pt=Motors_Car_Truck_Parts_Accessories&hash=item2a2e76205f&vxp=mtr
I would suggest that you and your mechanic together lift up the car, take a led-flashlight, and go through all the bushings. There are 2 upper control arm bushings per side that are prone to crack and squeak on these. They cost like 10e/each. We had some rattle and squeaking on my friend's A8 2005 that we got rid of by swapping those.

There are one rear control arm bushing per side, those cause squeaking, real hard rattle, shaking steering wheel at high speed braking as said, and can cause steering misalignment. Replaced those on my workmate's A8 1998 (D2).

The lower front control arm bushings seem to be really solid on these (in fact, they are quite solid rubber, so they often don't crack or cause problems.

http://www.ebay.com/itm/AUDI-A4-SEAT-P-SKODA-WISHBONE-LOWER-SUSPENSION-ARMS-16MM-8E0407151E-/381180907886?pt=LH_DefaultDomain_3&hash=item58c027116e

I'm going to replace my upper arm bushings on my current A8L 2008, because they squeak sometimes. Had same problem on ex. A8L W12 2006 at 245tkm. This now has 197tkm on the clock.

So check your bushings for cracks with a LED flashlight, if you see any cracks in the rubber, replace!