@Toralf
Correct, this has nothing to do with firewalls. This is more about better utilisation of slow circuits/relays by deliberately choosing to push relatively lightweight traffic across them. IRC and XMPP do not need 10Mbit/s circuits, not even close.
I'm not sure how Tor clients choose the relays they use to build a circuit, and I do realise that
a) there are probably more slow relays than fast ones b) attempting to pre-build both a "fast circuit" and a "slow circuit" will reduce the number of candidates for each.
I'm just looking for ways to drive more traffic across slow relays. :)
Best,