Source: http://forums.steampowered.com/forums/showthread.php?t=1011214
I just wanted to post a quick note to those users of net_graph 3 & 4. This analysis appears to use a lot of CPU time, and it is not at all threaded out. As such, if you're using one of these options and suffer from poor performance, try dropping down to 1 or 2.
In my own experience, this nearly doubled my frame rate. I went from an average of about 18-22 fps to 45-50. I now have peaks close to 300 as well which never happened before.