MP4.2+6.0

#14 is the torque control mount I was talking about, and the mechanic's visual inspection confirms the same with the oil leaking. It is an engine mount that deals with engine twisting under load. That will give you some vibration from my own 2000 A6 4.2 experience, plus my 2006 W12 similar experience.

On earlier ones like 2004's many get codes on the main mount solenoids. I think there may be a TSB about wiring. Your visual says no leaking so they should be physically okay. Try just physically unplugging them and then plugging back in again. If you get a "real" VAG COM instead of the rip off ones, you can run the self test that clicks the solenoids in the main mounts themselves to test. On my 2000 4.2, it showed a bad solenoid per the scan, but I was able to test it like that to show it was fine and thus didn't spend a bunch of money on a needless repair; I just did the torque one I needed. An absolutely classic example of why the rip offs and generic stuff are pedestrian and can cost extra repairs, and the real one has good value. You get what you pay for... Q.E.D.!

wanamees

MP4.2+6.0, I totally agree with your point of view - I always prefer original and working solutsions

Car is at the service atm - they looked through electricals and everything seems to be allright.
New spark plugs are put in - just in case - as they don't cost much and I dont have the info when they are changed (all the 7 year paperwork is at home).

Next step: Will change the broken torque mount - to see if it fixes anything.

This is just a theory, but they also suggested there may be something wrong with fuel injector(s). But shouldnt this usually lead to more severe problems like misrifes etc?

MP4.2+6.0

1. Torque mount should smooth out motor, and NOT replacing it will lead to more stress and potential for breakage of main mounts. If you have a timing belt job pending anytime soon, you might want to combine it or at least discuss with shop. Opening up room in the front of the motor in general makes getting at that torque mount much easier.

2. Before anything fancy with the fuel injection, just try some basic injector cleaner. In USA it would be a brand like Techron that cleans both the injectors and the valves; depends on what is sold in your locale that has a good reputation. And no, unless fuel is way off you shouldn't get a misfire. You could get some power output differences by cylinder with mixture differences in theory, but anything significant should get picked up by the oxygen sensors. Net, try some cleaner, but unless you see fault codes I would not bother much more. Certainly replace the air cleaner too along with the spark plugs, if you haven't already. Fuel filter would also be a good idea if you have no prior record of it being done; it isn't on the factory service list.

wanamees

Thank you MP4.2+6.0.

Torque mount will be replaced on next monday - I have my fingers crossed.