I just bought my first Audi, it's a 2000 A4 with the 1.8 l and 5 speed tranny. The second day that I had it it started to shudder and shake while in idle. The cel also started to flash. The codes it read were p0300, p0303, p0304, and p0411. I replaced the spark plugs, no difference. I also looked for a vacuum leak as I was told that could potentially cause this; but I couldn't find one. I'm planning on replacing the coils as well...but I'm not sure what else it might be? Any help or advice is appreciated.

**shuddering stops or at least decreases at higher rpms**