Use Maximum CPU Processing Power

How do I set the client to use maximum processing power of the CPU rather than the idle times? I run just the F@H client for hours so I think this should make it a bit faster.

If you've set it to use 100% (default setting), it will use up to 100% of the CPU.
If the CPU is totally idle, F@H will use all of the processor, so there's no way to make it use more.
If you want it to have a higher priority, you can manually set it to do so, however this will interfere with your other processes.