cl_showfps 1 to turn it on
cl_showfps 0 to turn it off
net_graph 1 Shows basic connection info
net_graph 2 Shows the complete connection info but my fps goes down by about 60%
net_graph 3 Is prob best, doesn't affect fps or ping, but shows everything you need
net_graph 0 to turn it off.
Sorry but for some reason I've never tried net_graph 4, so i don't know what it does.