I have exactly the same problem as I have stated in other threads. Sometimes my car just feels gutless, and it keeps going into limp mode in very inconvenient places. Last time it happened was Friday as we were driving back from the Highlands to Manchester. As it happens, my sister was following us in her MINI which was also having problems, so I was driving that for a while whilst my wife drove the Audi. It was whilst I was following my wife that it happened, just as she was overtaking a truck on the motorway. It was lovely to see her try and cut back infront of the truck to get to the hard shoulder with our two very small children in the back!! (coincidentally, I was at that very moment telling my sister all about the problem.)
It is going in on Tuesday to be looked at. It has been in before, and the EGR valve was very coked up. That was cleaned and then the car didn't do it for a while, and felt much quicker. The problem returned however. It always seems to be in similar conditions that it does it. Usually under very light acceleration on a slight incline. I've found that I have adapted my driving style a bit to compensate, by dropping down 2 gears into 4th for inclines on motorways, just to keep the revs higher and stop the car struggling.
When my car was in Audi for its 4 new injectors the other week
, they read the logged fault code (which I already knew) and did an hours diagnostics on it, then came up with some stuff about the turbo was stiff. It wouldn't spin freely. They then quoted me £2500 to replace it. When I stopped laughing, I left the dealership.
I'm still convinced it could be the EGR, and hopefully my very trusted independent garage will confirm this on Tuesday.
Another thing I have noticed, is that the DPF seems to be regenning a lot more than normal. I put this down to the possibility ofmore crap going through the exhaust if the EGR valve is stuck open, or opening at the wrong time, therefore clogging the DPF up quicker, and bringing on the regen. I suppose this could also be the case with a failing turbo.
Hope this helps.
MMM