Run multiple »
speedtest.net tests throughout the day to get a rolling average going - doesn't need to be once every miute or once every 10 mins - just keep doing tests on and off. Make note that no single speedtest.net server is ever truly stable as there's hundreds of people out there doing speedtests as well.
Also, you'll need to provide
as many tracert's as possible to see if and where there are failing routes. Run traces to yahoo, google, microsoft, dslreports, any of your favorite sites as well during the time of congestion and during times that there is no congestion.