Are you talking about the profile dropping by 200kb? Or sync speed?
The answer is that yes, a faceplate will probably cause some reduction in speed - maybe just a few kb or maybe a something greater. The faceplate itself (and indirectly the extension wiring and phone) changes the impedance across the line - lowering it slightly so bins which are borderline may become unusable.
I did some measurement many years back on my old ADSL max service and was loosing a few 10s of kb, tried a colleagues and they lost nothing (syncing at max with plenty of margin) and another colleague dropped about 120kb.
All you can do is make sure the connections are clean and tight, the extension wiring does not get too close to either mains or noise sources and if your phone will work without, remove the ring wire.
M H C
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