Just wondering how you got on with this? As it happens my line has developed an audible crackle again today, and surprise surprise my internet has also become unstable. In fact I can knock my DSL connection offline simply by making a phone call.
I'm glad I recorded my stats in this thread the other week as it gives me a comparison. On 12th March my downstream attenuation was 61 with noise margin of 15, sync at 2785. Right now, I have attenuation 62, noise 6, sync 3552, although I'm expecting that to drop while it tries to find a new stable level to work at.
The noise has been as low as 2 or 3 this afternoon. My reading up on the subject suggests that it should be between 6 and 15, so in a couple of weeks its shot from one end of the acceptable range to the other, and is now occasionally dropping right below it.
I have deployed my usual strategy - complain to BT about the audible noise on the line rather than arguing with VM about the intermittent dropping of my DSL service. Hey presto, BT engineer booked for tomorrow morning. I'll let you know how it works out.