BillFord reports that his IP Profile is quite unstable, but adjusts upwards much more quickly than the IPStream and WBC ones.
Whether there has been a target noise margin effect on your line would only show up with one of the VDSL routers that have been tried by others.
That could give rise to an interesting conversation with support if it did show it had been raised.
You: My target noise margin has been raised due to a faulty modem that you gave me.
Them: How do you know that Sir?
Y: I used a VDSL router of my own instead of your modem.
T: You are required to use the supplied modem at all times Sir, so you have broken the terms of your guarantee. Goodbye Sir.
Seriously I expect if there has been an effect it will correct itself more quickly than the old system as well.
Will this be your third modem then?