Hey, hope anyone can guide me to the right direction, as I've read a lot of threads but they are either dead ends or different issues. I drive an 2005 audi a6 c6 3.0 tdi (165kw quattro) with almost 280k km. And for the last month, when engine is all warmed up, it will suddenly get louder while i'm slowly accelerating in 4 and 5 gear. Once it gets to 6th it stops. Only happens under load. When i take my foot off the accelerator the sound stops. I found a video on youtube with the exact same problem, but no response there, so I hope someone here could help me.