could you please post what type of level7 firewall do you use to filter p2p traffic?
MT cannot efficently mangle all p2p traffic (please look @ http://forum.mikrotik.com/viewtopic.php?f=2&t=18024
), so the procedure normally used is to mangle all other traffic (e.g. calling it "known" traffic) and consider all the other p2p traffic.
Unfortunately this makes management of "known" traffic verfy complicated because it is not made only of software with ports < 1024, but many other ports are used (msn, vpn, voip, custom applications, ...), so customers continuosly write emails or make phone calls asking for ports to be opened.