I just purchased a A6 quattro avant 3.0 v6 awd for my wife to drive. It was missing when I purchased it. Scan showed misfire on 2,3, and 6. Replaced coil packs and plugs, no change. Replaced crank case vent valve (diaphragm was cracked), no change. Injectors appear to be working and test at 13 ohms. At idle the rpms will pulse between 600 to 1200, and after a while it will die. Really need help to figure this out. The car is in really good condition and I can not afford to take to a mechanic right now.