There is no way i know of speeding up downloads just ways to stop bitcomet from limiting your download speed.
By going into options, preferences, and in the generla tab make sure there is no limit on your max global download rate, secondaly maximise the number of simultanious tasks. If you are using a proxy then find a fast one as some limit you to a maximum of 128 or ever 64 kbps.Finally in the TCP/IP limit tab increase the new half-open limit.I’m afraid thats all i can think of atm.