http://www3.towerhobbies.com/cgi-bin...&I=LXD741&P=ML

I can't imagine anything getting through one of these. Maybe the slivers came from another source after the filter.
Some planes I don't use exhaust deflectors or filters on because they run so much better without them. When my clogs occur, I just remove the needle valve
and it flushes out on it's own. My symptoms are usually more severe.

If you haven't tried one of these filters, maybe it works better than the screen type.