You still having problems Marco, I would think it's time to do the fuel accumulator, fuel pump, lift pump, Injectors, Fuel lines and relay matey!
I have also heard of a fair few people undoing the fuel return line that goes back to the tank, taking the fuel cap off and blowing the return line with an airline to solve many strange K-jet problems. Seems these get gunked up and stop the flow in the metering head.
Have you had the timing checked and changed ISV and ISV control box behind the dash?
you can pressure test the fuel using a gauge inline with the system, I had a link to all this info but lost it when I killed my PC.
I had a similar problem with mine it turned out it needed setting up correctly on a RR went from 93 - 149 BHP but showed no signs it wasn't set up properly apart from start and idle problems. I would deffo get the timing checked as you say it sounded as though it was running on 3, many times they drop out but still run ok as they are German built and mere things like timing don't bother that engine!!
How old is the fuel in the tank if it is more than 6 months old drain it for the missuses car and put in a tank of fresh petrol.
Also have you recently put any GSF temp senders on your block as I and a fair few others have had serious problems with them which were cured by spending more on a VAG part. As one tells your ECU when the engine is cold or hot one tells you on the dash and one controls the WUR you could try changing around the dash one with the other two just be careful the connectors aren't right cracking!!
good luck!
