Up until recently I have had horrendous lag in FTB packs and I have discovered an extremely effective fix. The way to get rid of the lag is simple but effective, Linux! One day I logged in to my computer and it told me that hardware connected to my computer was not functioning and refused to let me log in. I rebooted the computer just to discover that Windows Vista couldn't boot up! I decided that i would convert to Linux. I did some research and found that a "flavour" of Linux called Ubuntu(www.Ubuntu.com) would work on my computer. a few hours later I logged in to my FTB server to discover that my FPS had gone from an average of 6 to 35 (optifine, render distance tiny, etc.) a few days later i wrote this up to share my fantastic discovery!