kernel_task eating a lot of CPU on mojave
You do not actually want to remove the IOPlatformPluginFamily.kext - that is a really bad idea.

When you see kernel_task seemingly (!) eat a lot of CPU, it actually means that the operating system is throttling CPU usage to prevent the system from shutting down unexpectedly. This happens when you have a problem with the cooling solution in your computer.

You want to ensure that fans are operating properly, vents are not blocked, thermal paste is still OK, etc.

If your cooling solution is OK and this problem persists, you might have a problem with the temperature sensors or the main board itself.