what's your problem: have you events with EventCode=5137 OR EventCode=5136 OR EventCode=5141 or not?
if not, did you checked if GPO events are logged (by default this logging is disabled!)?
If instead you have events, check if the problem in in the match with ldapfilter (in other words, see what result you have without ldapfilter).
In addition, for my knoledge, the EventCode for policy changes is 4719.
At least, usually WinEventLog:Security events are in the wineventlog index, so you don't need to search in all indexes (your search is slower!).