Hello, I have a 2006 Jetta TDI (BRM) which has acquired a shudder. The shudder occurs immediately upon acceleration or when trying to maintain speed. When accelerating from a stop the car will accelerate and then fall on its face for a second and proceed normally. Usually when the shudder occurs during acceleration it is followed by a puff of black smoke. When the shudder occurs while trying to maintain speed it is typically below 2000 RPM. Typically it will also occur after the car is up to operating temperature and more often when the weather is more extreme (i.e. high temperature). The car has had the timing belt replaced at 100k and now has 104k on it. The car has a Kerma ECU tune but the shudder occurs in the stock and modified settings. The torsion value post timing belt change has been confirmed to be within the recommended range (with VSDS). Does anyone have any ideas? Any suggestions are appreciated, thanks!