I used a couple of sites a few months ago to tune my connection, and it helped the download/upload performance of my adsl connection in the house.

The overall picture is described on the max dsl diagnostics page. On there I use DSLzoneuk to monitor performance from a uk based site, but I use dslreports in the US to check tweak settings.

Usual caveats apply – not my fault if you break something by changing it as a result of this posting..