When the few tones at the end of the upstream are disabled, the downstream snr is higher, and can sync at a higher speed. With the tones enabled 2016kbps at 4.0db, 2272kbps at 4.0db. This comes from disabling tone 24 to 32. Whilst still having the same 448kbps sync. Why does the upstream connection affect the downstream so much. Some tones gain 3db just by disabling these tones.