Yes, interleaving depth on FTTC can often be into 4 figures, and interleaving also typically drops the sync by about 10Mbps.
Two things are strange though.
One, it is also normal for attainable to increase considerably when interleaving is introduced. In other words the sync and attainable move in opposite directions, and converge to very close together figures when it is removed. Both having fallen is unusual.
Two, I wonder why your weren't on interleaving using the Billion. Do you happen to know which make of FTTC cabinet you are on? Has your latency risen by 8ms?
Edit - I wonder if you were on G.INP and the modem swap has removed that? In which case it should return in time.
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Edited by RobertoS (Wed 11-May-16 23:26:32)