Slow filters in HPL

Is it just me or can HPL be incredibly slow at evaluating complex filters? I have two unload jobs on the same table, one of the complete table and one which eliminates any of 100 or so row types older than a certain date. The filtered one goes orders of magnitude more slowly through the table. I'd put the criteria in a table and join to that but I can't get our version to accept joins (at least not through ipload). Is there something I should tweak or is HPL just simply bad at logic processing? Andy Kent