In reply to a post by RobertoS:

If you used to sync at 8128 and now it tops at 7616 it is almost certain Interleaving has been turned on automatically by the system due to errors occurring while the cable was being messed around with.

It will not turn itself off, even on an auto setting - that just lets it turn on. If you are unhappy then contact your ISP support.

IPStream always syncs at a multiple of 32kbps.

It's currently at 7488kbps and i opted out on the interleaving. In fact the Zen control panel says it's off and also DMT indicated I'm in Fast path mode.

Interleaving was always set to Auto and infact has been off for over 4 years. It's only recently since the gas board dug up the road (followed by BT's new cable) that interleaving was automatically switched on, which did change my sync speed to 7616kbps. However the Zen customer portal/control panel showed numerous entries of the same thing, ie just duplicates (exact same date & time), so it was hard to see what was going on.
After it was switched on whilst in Auto mode i opted out and the speed re-synced back at my 4+ year norm of 8128kbps. Now a few weeks on the line whilst still in Fast Path mode has dropped in Sync speed since BT changed the cable.