Had a problem with P0400 Generic EGR fault for about a year now. started with spanner of death light on the dash and car going into limp mode. this happened a few times over a few weeks so checked EGR Valve and cleaned it all OK for a few days till a nice long run to Wales ended in limp mode in torrential rain in the third lane M4.
So lip bit i relented and got a good 2nd had valve of FleaBay for 80 quid, again all fine for a couple of weeks but the fault returned. Bigger bite of the lip and a lightend pocket but with a nice shiney EGR fitted later i thought the problem was solved.
Car ran fine but was always hesitant at 60-62 MPH until you guessed it old limpy mode reared its ugly head again.
Now this is where this site is invaluable as ive heard about the "swirl valves" in the 1.9 but not the 2.0 2.2 dti.
So took the EGR valve out to see how much soot had built up and BINGO a huge piece of carbon came away with it from the inlet manifold which is in two parts, removed the top cover from the manifold and what i can only describe as what looked like a carbon filter inside the manifold with four small holes in it ?????
Turns out that this filter was a build up of carbon and the small hold were what the inlet "Butterflys" were trying to breath through, It resulted in me carfully chipping away with a screwdriver and a hoover to suck out about 1kg of build up before finding the 8 bolts that hold the manifold on the the block after removing the manifold and steeping it in a bucket of paraffin overnight (There was 1 inch sludge at bottom of bucket).
Next day with a nice shiney free butterflys a clean manifold and cover back in place the car runs with a power increase of 1000% and MPG up but more importantly no EML spanner. Over a month now and the car runs like new, incidently the dealer did point me in the right direction but quoted near £1000 to do the work.
Just thought i would give somthing back to the website help someone with similar problem.