I have a Macbook air (4.2) 2011
I had trouble installing 10.11 - so insted I installed from time machine backup. It is very slow. Acti-moni reportede "kernel_task" use up to 500% cpu. Rebooted into Root user and with safe-boot (shift) - that made a considerbly different - now "kernel_task" just about 1%
There is no 3 parti connections - no usb
Apple Hardware test - reportede no problems
Micormatic - mactest - also reported no problems
When i boots and works fine in "safe-mode" i think it is software relatede?
Could i try your fix? or is there other solutions? -have i overlooked something?