Right so I have a hugely confusing problem with my car......its an Audi a3 1.9tdi 2004 8p with 95k on clock A year or so ago the engine light came on so I checked it and it was the egr fault code p0401. Left it and didn't do anything for around a year because the car ran perfectly fine. A year on and the car all of a sudden started black smoking with a intermittent pause before getting normal boost and power. So I would pull away and I would get a drop in boost for about half a second and then all of a sudden the power would come shooting back along with a cloud of black smoke. So I replaced the EGR... fully cleaned all the pipes and as much as I could of the intake manifold using mr muscle etc. Problem still there.....so I removed the egr vacuum pipe and blocked it off with a screw.....CAR RUNS PERFECT! So I decided to check all the vacuum pipes for any leaks etc and everything was all good. Anyway so few months went by and I decided to try and fix the problem.....went and put the egr vacuum pipe back in the egr and tried driving the car and it wouldn't drive at all! just stalled when trying to pull off!!?? If i revved the car at stand still it wouldn't go higher than 2k.....and the revs were jumping up and down whilst revving (cutting out). Also was getting loadsss of white smoke out the back! Ive checked everything I could think of, even checked air filter and replaced the MAF because I thought it was that, no change. Someone please help!? One question.....is it ok to block the egr vacuum pipe off and keep the car running like that...? won't cause any back pressure and damage anything will it?? Thanks!