Persistent ADSL Problems

Firstly I hope I am posting in correct forum, if not forgive me. Anyway I have been having speed problems with my line. Name I am having low sync events. The source of the events is at the moment unknown. My ISP ,newnet, have been helping me however these problem has been with me since late June so I thought you guys can help.
I have tried the following to cure the problem.

Purchased new filters and modem/router.
I have rewired my two extensions and fitted new face plates.
I have replaced the faceplate of the master socket with a new filtered plate.

I have ensured that the router is away from any electrical devices.

BT have come round twice now and both times have told me there are problems back at the exchange (I.E there are no problems with my home wiring) Each time BT get my IP profile altered to the max speed that my line can take however each time my profile falls through the floor.

Between me and the ISP we feel there is noise on the line somewhere, a REIN engineer has been mentioned but as yet I have hear no more. My actual phone line is noisy with crackles and hissing with the occasional digital bleeps faintly heard in background, what really puzzles me is that the noise is not present in the morning or late evening. BT state my line is OK. Can anyone suggest what I can do pinpoint source of interference as my BB experience is terrible at present.

Any help appreciated, Mark Durham

Can you identify a time of the day when the line crackles? If so do the quiet line test (17070 option 2) during that period with your ADSL kit disconnected from the line. If you're lucky and you hear noise report it straight away to BT as a voice line fault.

If you have a test socket could you post your router stats both in and out of the test socket?

See http://www.dslzoneuk.net/socket.php?type=html and http://www.dslzoneuk.net/adsl_line_stats.php