Hi, I have a 1999 a6 2.8l with 130 000 miles on it. A month ago my car started to shake around 1500 rpm at low speed, and at high speed when I stop pushing on the accelerator. I changed the sparks plug, rebuild the first part of the vaccum line "i found a lots of dust in the hose", after putting the new plugs, the shake seems to have gone away. But now it's getting worst, it's like the clutch goes on and off, like the ecu can not figure out to stay in 2, 3, or 4 gear. Maybe neutral I really don't know. The strange thing is that when I drive the car in triptonic, even if I upshift quickly, the car drives perfect, maybe a little ruffer than before when I shift, but it does not shake at all.