I’m not technical so don’t understand any of this but:
Recently, my old Netgear modem/router died.
I replaced it with a DrayTek Vigor 120 modem, plus a wireless router (AirPort Extreme, but that’s irrelevant).
My wired internet speed suddenly jumped up to 14 mbps (or whatever the unit is), from 0.5 the last time I ran the test. I was averaging about 3, I think, at best.
So I don’t know about this cleaner thing but I suppose the first thing is to check your modem. I guess it’s this ADSL2+ compatibility that’s important, going by the post above. Was news to me.