1) Have you purchased the manager's manual yet?
2) Please post the vicidial version AND BUILD (you were close!)
3) please also mention whether there is any other software on the server.
I note that you say server load 8, but you failed to mention on which server. I am left to assume it is the asterisk server (i hate assuming, but this seems highly likely, so I'll go with it). You may wish to consider using the unused CPU of your other servers by using your MySQL and / or FTP servers as dialers or by simply adding another asterisk server.
I believe the managers manual details setting up RAM recordings (which would be why i asked if you purchased one yet).
However, recording calls IS CPU intense and you may find that configuration does not resolve your lack of available CPU on the single asterisk. so ... combine MySQL and apache and recycle the mysql machine as an asterisk server, perhaps the ftp server ... check all your CPUs during "high use" and see which one has some (or a lot of) available CPU. then stop wasting it