Troubleshooting high load
Here are some troubleshooting steps:

Run ps aux to see which ones are actually running real time.

Next run the iostat to watch the actual CPU loading and see if you can determine if some new processes are running and whether that is increasing or decreasing the IO and CPU load on the system.

For comparison here is the output of the iostat I have.

disk0           disk1           disk2       cpu     load average
    KB/t tps  MB/s     KB/t tps  MB/s     KB/t tps  MB/s  us sy id   1m   5m   15m
   26.55   3  0.08   177.96   0  0.00    65.01   0  0.00   3  2 96  1.16 0.96 0.90


Some Git and Homebrew are know to create the problem so check your versions to latest update.