throttling

I have a 2Mbps connection. Speedtest.net shows 2Mbps up/down Fast.com shows 1.7Mbps down While browsing the web or downloading from sites like sourceforge, i get around 170 - 250KBps speed. In torrents, in the starting it hits 250KBps for 1 minute or so and then falls down to 70 - 90KBps and...