csf has a tendency of consuming resources however 20% is not a significant change.
However in future you can (not a must) change config values as below
LF_DIRWATCH = "0"
CT_LIMIT = "0"
LF_HTACCESS = "0"
LF_MODSEC = "0"
LF_DIRWATCH_FILE = "0"
PT_LIMIT = "0"