As youv'e changed routers, one point worth loking at, are you using the same lead from the microfilter to the router ? If your using the new one for the new router is it still coiled up or sitting predominately around other transformers/mains cables.
This usualy dosn't make any difference but some times you may be picking up some noise via this lead because in a typical set up this may be clumped togeter with other transformers mear the mains supply.
Also a lot of people will coil any spare cable up to keep things tidy. Avoid doing this with the dsl lead from the filter to your router/modem (also the same with any data cables such as the ethernet cable). Best practice lay this cable out as long as you can, maby back & forth a couple of times, away frombeing directly by any transformers and not running parallel within 50mm of any mains/power cable if you can.
Also some times it may be wrth trying to move the cable/router modem away from any plumbing/ pipe work in case this makes a difference. sometimes if something electrical is dumping current back doem the earth, then this can be retransmitted via metal plumbing.
As I said this isn't very typical but might be worth trying, it's a nice easy fix when trying the above youy suddenly find, Hello my stats/sync have improved.