HI, all. my first post here 
I have a late 2008 A4 B8 Avant, 143PS.
I have this problem for second time.
First on 30 000 km. They changed my complete clutch and flywheel at Porsche after 8 visits and 10 days total in the service shop. I did not pay for that.
Now with 105000 km, same problem. This time I went to a different service, with some friends of mine. We think the problem is in the self-regulating SACHS pressure plate. It is somehow stuck and can not adjust. So when the friction disc is worn out a bit, it can not fully engage. Other interesting thing is that the clutch bearing is almost gone. I never keep my foot on the pedal!
When we disassembled the clutch, is looks as new. Without any wear indications.
Anyway, here is more to read from the SACHS www site for the clutch pressure plate:
http://webcat-services.zf.com/…00+970+019&EINSPNR_ART=32
Here is a brochure about the pressure plate: http://webcat-services.zf.com/…ge/0032004_SIPkwXTend.pdf
It is the so called "XTend" plate.
I would appreciate any ideas as well as I am stuck with a nice car and a stupid problem.
One more thing, my clutch slipps at 5 and 6 gear at about 2300+ RPM, usually on the Autobahn when the Nm is biggest.
Here is a pic of the assembly we took out of the car: