It's not related to the MU module, same goes for hotfile. It's not "at some RL scripts it works" it's cause of routing to USA/Hong Kong.
For example if you use FTP upload from europe->hotfile, you still get 500KB/s max.
On megaupload, if you use MU manager or something else (i've tried them all..) I still get 200KB/s, it's not related to rapidleech, it's the distance between your server and the MU/HF one