I encountered an HTTP/1.1 400 Bad Request for a feed that existed and validated. After a bit of research I found that by the time the URL had been called by the Snoopy include the URL encoding had been stripped. The %20 (spaces) were now just spaces.
On line 135 I wrote
$TEMP_URI_PARTS_QUERY = explode("=", $URI_PARTS);
$URI_PARTS = $TEMP_URI_PARTS_QUERY."=".urlencode($TEMP_URI_PARTS_QUERY);
and now all my feeds with GET variables with spaces WORK.
Hope this helps, enjoy :)