Go play around on the dslreports.com tests. They work for anything, I use them to test and tweak my cable modem connection. The
tweaks section can test and show what tweaks should work good, you may also want to do a
speed test to see how fast it says your lines are. Then you can go to the tweak that really works (MTU is a bunch of crap), adjust your
RWIN setting with the provided registry tweaks. You may want to read all the technical junk though instead of using their 60 second solution, since if you open the RWIN up too much it will also cause problems. By adjusting my RWIN window from 16KB to 64KB it sent my connection from 40x a 56k modem to 60x a 56k modem. However, if you have lots of packet loss on your line it isn't the best tweak to use, since you will be losing larger packets of data, slowing things down even more.