first of all here and try the klr2.5.0 or k-lite2.6
but let me say first of all that your version has nothing to do with speed, however there are updates that you don't have with 2.4.3 so update to which ever one you like.
now your problem is your sources boss remember:
your download speed depends on the # of sources for it and their upload speed, anddon't be fooled by whatyou see in the search window they are not an indication of who is available for connection so change supernodes to see if you get lucky, also use localized supernodes, also try changing ports, and lower your upload bandwidth,remove the no ip sources from your dat files and see if it helps , and if you have a router you need to get kanat