I know the purist problem. I'd also use silicone only as a last resort.
On my idle problem earlier - Actually the fact that the symptoms are changing means I am getting closer and closer to the real cause. For example, the fact that it is now rough when in Park, AC off, warmed up (same missing sound as before), regardless of RPMs, and smoothes out when I am in drive, rules out a bad fuel supply (we'd be even rougher at the lower rpms, but it's perfect there). The idle air valve should not be affecting this. However, a dirty idle air valve could have skewed the entire system enough to mask the underlying causes. I think in my case it was a number of problems, and they are not all resolved yet. But I feel more and more certain it could be a bad throttle idle actuator switch (there is a technical service bulletin out - it causes irratic idle rpms) or actually a bad transmission/reverse light switch. The latter seems to make the most sense - I sometimes get a strange hesitation when I restart the car and put it into gear, only when warm, only occasionally, and only for a split second. The tranny engages right away, but the engine seems to lose power for a second or two. I interpret that as the engine having a slow time realizing it's in drive.
The fun thing is now I am begining to narrow it down, and the diagrams are beginnig to be of use....
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)