Internet while downloading.

Oh my bad. It is connected directly connected to the modem(Although it was the same problem with the modem+router). I'll try out what Fiel said. Because I only limited BitTorrent.

What you also can try, is limit the maximum -number- of connection allowed by bittorrent. Some connections are capped by a lower number of concurrent connections before the ISP is throttling them automatically. Try 50 max, or even 25.