Increasing PHP CPU Efficiency

I'm running a WAMP (2003, 2.2, 5.1, 5.3) stack and am seeing high CPU load when running a third party, open-sourced application.

Are there any tools to increase CPU use efficiency for PHP or profile what code causes the CPU load to spike?

From serverfault Omer van Kloeten

• Try one of the php accelerators like eAccelerator.

  Omer van Kloeten : I'm already using the Zend Optimizer+, which has increased efficiency, but only slightly...
  From David