In current releases of IPS software (starting with the release of the E3 analysis engine); high CPU in and of itself is not a good judge of sensor performance. A better indicator is the "Inspection Load" (big speedometer on the home page). This looks to be just over 10% in your attached screenshot. The reaoning for this is a change in interface processing implemented in the E3 analysis engine. From the release notes from the E3 release:
The E3 engine software contains changes from CSCsu77935.
The resolution of this defect modified the sensor's idle time algorithm,
applying additional CPU to polling of the NICs to decrease the polling
interval and reduce latency. This results in the CPU usage being reported
higher than previous releases, including by external tools such as top and ps.
This additional CPU load can be noticed on single-CPU platforms, as well as the
primary CPU of multi-core systems.
Since the additional CPU load that is reported while polling is actually
available to process packets, and reduces as inspection load goes up, it does
not negatively affect the overall throughput of the IPS.
The best indication of sensor load is shown under "Processing Load Percentage"
in the "show statistics virtual-sensor" command output and IME Home Page Dial.
If there is indication of impact to traffic traversing the IPS-4240, then it would be beneficial to open a service request with TAC and provide the full output of 'sh conf' and 'sh tech' for review.