hi everyone ive just bought an a3 tdi 1.9 06 model with just 23000 miles on the clock with full history. Every couple of minutes when driving at around 2000 revs you put your foot down and nothing happens, the revs drop slightly followed by thick smoke out of the exhaust which is driving me crazy, i disconnected the maf and the car drove great with good acceleration and no smoke. i decided to replace the maf but its just the same if not a bit worse. dont understand what the problem is. only bought it last week but the car has sat unused for several months due to the elderly owners eyesight failing. ive been told it could be unburned diesel in the exhaust system or a faulty turbo boost valve control ? please help been on a few audi forums but they havnt offered any advice. many thanks