Hello. I recently had a monessen DFS36 ventfree fireplace installed. The contractor accidently put all the lave rock onto the burner plate instead of the fireplace floor. After moving the lava rock to the fireplace floor, I noticed there was a lot of rock dust on the burner plate so I vacuumed it up. The fireplace now whistles when in operation at higher settings. The manual says this may be because the burner ports are dirty. That could be because a bunch the lava rock dust got in there. Anyway, does anyone know how to clean out these ports effectively? I've tried vacuuming them out but the problem persists.