Are you on a fixed line speed ? At that attenuation 6db should give you 4000 down load plus. Presume you have tried the test socket. On the variable adslmax system the download speed will adjust to a level which gives 6db (normally) which will then trail down a bit after dark as am radio interference kicks in. So its the download speed which is the variable not the SNR. On wiring, its transmission line theory and you don't watch an impedance mismath anywhere on your wiring ( ie no tee junctions). The I Plate is only the same as cutting the orange ring wire anyway. Tried the solwise and adslnation sites ?