i don't think there are many changes we can make that will really help to much but you are more then welcome to try, i will assist in any way i can for starters read
this post: https://testmy.net/ipb/topic/934-vanburen-testmynet-cablenut-settings/
and this one: https://testmy.net/ipb/topic/1984-sticky-stop-before-you-post-your-problems-read-this/
try some of the things listed in those posts, i'd start with downloading TCPOptimizer
~ TriRan