Does contention at exchange alter sync rate

[#1]

I know that contention at the excahnge will lower the overall through put of a connection but will contention itself reduce the the lines sync rate or is sync mainly down to line quality?
My understanding is that the sync rate should not chnage dramatically but speed of the info down the line will if too many local people are using the return path to the same isp.
Podman

[#2]

Exchange contention will have no effect on your sync speed.
The sync speed is negotiated between your modem and the DSLAM.  Contention affects the backhaul from the exchange to BT's network.

[#3]

Just to echo what Paul has said - exchange contention has no bearing on sync speed whatsoever.

[#4]

Cheers, I was just querying advice given in response to a raised ticket.
Podman