For VbScript you can do a split on the comma into an array then only use the elements you want to create the new message:
msgarray = split(Fields.VarCleanMessageText,",")
wantedfield1 = msgarray(6)
wantedfield2 = msgarray(9)
wanteddata1 = split(wantedfield1,"=")
wanteddata2 = split(wantedfield2,"=")
Fields.VarCleanMessageText = wanteddata1(1) & "," & wanteddata2(1)
Then have a log action AFTER the script action.