This is purely an FYI/observation and not a bash or anything against those guys, take it for what it is.
Their header design places the primary o2 sensor in a single runner vs at the collection/collector point of the three runners which in my book and others is a no-no. When this is done the engine is making air fuel ratio changes based on a single cylinders readings, for all three cylinders on that bank instead of making a "global" adjustment based on the reading from all three (making them all run as evenly as possible by taking a reading from all three) This can in turn have the other two cylinders not monitored running rich or lean depending on the monitored third cylinders readings.