Lag issues?

My fps jumps from 19-57, depending how many people are in the room. I lag very badly when my fps gets pit bottom and it is making me die constantly. (bullet pattern goes crazy after the first shot.) I turned my graphics to the lowest and it still lags at the 8v8. I like large rooms. I also have a 2g of RAM, so thats not a problem. My internet is also top notch. (verizon fios.) I also use game booster, so I can lag less. It still lags sometimes and it is annoying. Anything I can do to fix this? Thanks for the help.