You can either buy a standard ordinary faceplate if yours has been binned, and use the dangly, or get a BT filtered replacement one, probably either is available from places like Maplin, or get a "high-quality" one from ADSL Nation or Clarity. Though see my earlier comment about the XTE-2005.
Before I got the XTE-2005 I tried a surge-protected one from Maplin. That was dreadful and went straight back.
It's odd the sync stayed the same but the noise margin went up. Keep an eye on things.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost.
Internet connection - O2 Standard.