I´ve been looking /etc/mail/spamassassin directory and there are some files v310.pre, v312.pre or v320.pre that load some plugins.
Maybe one of these push the load high, If anyone recommend to turn some of them off, I would like to hear comments:

This is what I have enabled by default:

Perform DCC checks
Perform Pyzor checks
Perform Razor2 checks
Perform Spamcop reporting
Perform AWL checks
AutoLearnThreshold
WhiteListSubject
MimeHeader
ReplaceTags
URIDNSBL
HashCash
SPF
ImageInfo
VBounce
Bayes
BodyEval
DnsEval
HTMLEval
HeaderEval
MIMEEval
RelayEval
URIEval
WLBLEval
URIDetail
HTTPSMismatch
Check