Hello I am new to the forums and would like to say hi.Does this vehicle have a 2.0in it?I worked on a 2006 2.0 A4 recently that had a similar problem, I found with the new 2.0's to have a wide array of problems. I have had a many valve cover breather recirculation valves to be failing causing internal vaccum leaks and then misfiring. One indication of this issue is with the engine running try to remove the oil fill cap, most time it is extremely hard to remove and once you remove the cap the engine will stall. I also had some ignition coils go bad on me. I also had a 2.0 not start because of faulty low fuel pressure sensor that the fuel pressure ingressed and shorted the sensor out causing concern. I also had the mechanical fuel pump follower wear out the cam shaft lobe causing fuel starvation issues. I also had a bad breather valve from the turbo pipe to valve cover. This problem also caused sporadic misfires.

Sounds like this vehicle has a bad valve cover recirculation valve. The faults that are in this vehicle will tell which is the problem. When this valve goes bad usually sporadic misfire faults are stored and fuel trim faults are stored.

 

Did they check the diverter valve. I had a problem with the diverter valve. It was cracked (plastic). Check engine light was on, car was running very rough, felt like it was running at half power.

 

Please add your location to your profile. A lot of us have Vagcom and experience in troubleshooting. If we know where you are and we are near we may be able to help.