Have your tried to use McAfee Profiler (https://kc.mcafee.com/corporate/index?page=content&id=KB69683) to track what's going on 'behind the scene' when CPU spikes?
"Client base method to Low" what do you mean by that setting?
If you are not on ENS 10.6 already that'd be the first thing to try, upgrade to that version.
If this is not possible and you are on 10.5.4, there is a HotFix that reduces CPU for Mfeatp.exe. See release notes below.
To check quickly if you have this HF already installed, the version should be: Endpoint Security Adaptive Threat Protection 10.5.4.4241
Hope it helps