Audi Repair: TDI 130 BHP HESITATION AND EXCESSIVE SMOKE EMISSION, pressure control valve, wastegate valve

Question
Hi there.Can you help?I have had problems when accelerating.Just before the turbo kicks in under acceleration load there is what feels like a misfire and excessive smoke coming out of the exhaust.This clears once the turbo activates and the car then accelerates as it should.I have cleaned out the inlet manifold and EGR valve.I have also disconnected either side of the turbo and checked that it moves freely.I have added a diesel flush in case the injectors were maybe partially blocked but if they were faulty surely the problem would be there all the time.All the vaccum hoses appear intact and i'm assuming that the boost pressure control valve is working as the turbo functions fine.The MAF sensor has been replaced but the fault is still there.The mileage is 129,000.There is no MIL light on the dash.I'm wondering if the wastegate valve is faulty or if the turbo seals are letting oil into the combustion chamber
??Do you have any other idea's.Regards...Dave Matthews  

Answer
Well this sounds like a tricky one.  Maybe your boost gauge or pressure sensor is not functioning right, it sounds like it is injecting too much fuel before the engine revs and boost are up there.  I'm not that familiar with diesel engines but it does sound like the fuel metering is off when you open the throttle.  Has this started happening suddenly or gradually?  Let me know,  Jan