Connection speed dropoff

[#1]

Any reason my my speed would now continuous connect lower than a couple of months ago? Previously I'd been connecting at around 3000kbps, now it seems I'm lucky to get 2300kbps, and it's usually around 2000kbps.
Latest BT test results indicated ip profile of 1750kbps, connection speed of 2304kbps and actual throughput of 1372kbps.
Could a filter cause the drop in speeds and yet still work?
The VP Capacity at the exchange is showing as green currently so there shouldn't be a problem there.

[#2]

It could do, if it's developed a fault. It's more likely that you've had a couple of interference related disconnections and that's dropped your profile.
Best bet is to unplug everything from the phone line and plug the ADSL equipment into the master socket, see if the sync speed improves. If so, you can then plug everything else back in one by one and check to see if the speed has altered after each, that way you'll find the cause.
If that makes no difference try unplugging electrical items to see if there's any interference coming from those.
Hope that helps,

[#3]

It could be caused by "Christmas interference" - when all those flashy lights have been put back in the attic, it is possible your speed will creep back up again.
A similar problem affects me - I've gone from 6500 kbps to 5500 kbps - I'm going to wait until the neighbours turn the interference off + 3/4 days for BT to decide that I'm deserving of a better profile.